After seeing some of the discussions on this board over the last few days (I know, I know, welcome to the Internet), it occurred to me that such a passionate fanbase might do well to take a look and, like true courtiers, retain our face and honor. During this post, I will only be using Rokugan-based examples, because using real-world examples can be inflammatory for some folks and that's not the intent here. I would encourage anyone responding to also limit their responses to Rokugan terms.

An argument is a connected series of statements intended to establish a proposition. I think this, I back it up with this series of facts, I present it to you. You look at it critically, ask for clarification or additional supporting information, and draw your conclusion based on what's presented to you. Too often, we look at the word "argument" as the word "fight". Civil disagreements and arguments are how human beings explore knowledge and come to mutual understanding; fights are how we cut off avenues of communication and refuse to understand another person's viewpoint. If you have been told since you were small that the color of the sky is green, you will naturally be challenged by the first outside view that posits that the color is, in fact, blue. To the "blue" person, this is indisputable proof based on evidence. To the "green" person, this is a radical challenge to a deeply held belief. If "blue" starts screaming at "green" about how stupid this is, "green" will have no interest in ever believing "blue", and you get an intractable issue - no matter how demonstrably wrong that view is.
Any debate naturally starts with two opposing viewpoints, and usually - as in the "blue and green sky" example, those are beliefs that people are attached to, either factually or emotionally. It's important to realize the following: at the start of the debate, both viewpoints are equally valid to the people maintaining them, and it is up to both sides to be open to the viewpoints of the other. If both sides approach the argument with the idea that their viewpoint is intractable and cannot be changed, than no progress can happen. The "green" person must be willing to accept factual evidence, and the "blue" person must be willing to understand the background of someone raised from birth to see the sky as green. All arguments take place in the realm of nuance; broad statements usually lead to one of several logical fallacies that can derail the conversation or prevent understanding. Here are a few of the most common fallacies:
Arguments usually have to follow a clear chain of evidence; a Phoenix Clan shugenja dropped an egg on the floor, this is why there's a broken egg on the floor. It cannot, however, follow the chain backwards - this is called a "post hoc, ergo propter hoc" ("if, then, because of") fallacy. There's a broken egg on the floor, therefore a Phoenix Clan shugenja must have dropped it.
There's also the fallacy of limited evidence, often called the "correlation equals causation" fallacy: every time a Kabuki Troupe passes through our town, a rainstorm follows. Therefore, Kabuki Troupes cause rainstorms. The Kabuki Troupe is much more likely to simply be passing through that particular town during the rainy season.
The next few fallacies are often called "deliberate fallacies" and have to do with people who get defensive in a debate and rely on some tactics that really don't help, and in fact hurt, understanding between the parties. A deliberate fallacy relies on the manipulation of the debating opponent and the audience to prove a point that they cannot prove factually.
The first is often called the Strawman argument. Now, it's important to understand that a Strawman Argument has a very specific definition - just because someone disagrees with you does not make their argument a Strawman. In order to be a Strawman argument, the person must make a declaration that misrepresents the current scope of the argument and re-frames it in such a way as to make arguing against it cast a bad light upon their opponent. For example, a Scorpion and a Unicorn are arguing; the Unicorn states that some of the taxes on the peasantry should be eased so that their people can make it through a particularly harsh winter, and the Scorpion responds with "Oh, so you hate the Empire and want to see it fail? Things are hard all over and you should do your part, just like everyone else." The Unicorn was presenting an argument for the betterment of their people, and that argument gets shut down by a Strawman arguing a different - although tangentially related - point that the Unicorn can't possibly respond to in a good way.
The most insidious of the deliberate fallacies is sometimes called the Texas Sharpshooter (I guess it would be Tsuruchi sharpshooter in Rokugan), named after the following scenario: a Texas gunman fires ten shots a barn, then goes and draws targets around the bullet-holes, giving himself a bulls-eye every time. This is the practice of starting with a strong viewpoint, removing factual evidence from context, and presenting it plainly to cast an opposing viewpoint in a bad light. Facts are facts, and the manipulation and cherry-picking of statistics is a very dangerous means of convincing others. For example, a Crane courtier dislikes the Lion and wants to discredit them in court. He produces a document that states that the Lion only sent three bushi to assist the Dragon with a Yobanjin incursion, therefore the Lion are shirking their duty to protect the Empire. The document omits the context that the Lion sent their three best Akodo generals and that the Dragon only asked them to send advisors to assist with troop movements, not to send fighting detachments. The facts have been manipulated to cast the Lion in a bad light.
Another bad Tsuruchi sharpshooter is to use cherry-picked facts to make generalizations about entire groups of people; for example, a Phoenix scholar produces a work regarding the state of education in Crab lands. A courtier that already believes that the Crab are much less intelligent than the other clans seizes on that to cast the Crab as brutish savages. The original work by the Phoenix scholar actually finds factual evidence that since the majority of the Crab's economy must go to support the efforts on the Kaiu Wall, they have little left over to spend on education. Due to economic factors, Crab children have less of an educational opportunity than the other clans - this does not reflect on their natural intelligence, simply their ability to access education. By removing the nuance of the Phoenix scholar's work, the courtier has deliberately picked and chosen facts that support that courtier's supposition.
And that brings us to Ad Hominem and Tu Quoque attacks. Put very simply, both of these tactics avoid engaging in the debate by attacking the opposing debater. With an Ad Hominem attack, the person attacks their opponent's character or person, undermining their argument without actually responding to it. For example, after a Yasuki courtier presents an argument for more funding for the Kaiu Wall, an Imperial advisor asks the court whether they should grant anything to someone who has been previously arrested by magistrates and can't even wear a proper robe to court. By attacking the person, not the argument, that advisor undermines their argument instead of responding to it.
Tu Quoque ("you, too") attacks follow the same idea of attacking the debater, but answers criticism with criticism and tries to appeal to people's deep-seated dislike of hypocrisy. Instead of defending their own viewpoint, the Tu Quoque user tries to shift the focus back on their opponent and paint them as a hypocrite. For example, A Lion courtier points out that the Crane courtier in the previous example did not include the pertinent facts from the Dragon's military request, and the Crane responds that the Lion courtier omitted other facts earlier in the debate. While Crane may be right about the earlier omission, it does not mean that the Crane is right to also do the same! This one is particularly tricky, because it's very good at triggering an involuntary emotional response in the audience and the other debater, which usually leads to the dissolving of polite discourse - which, of course, is the whole point of using it.
Finally, there's the use of Anecdotal Fallacy, Poor Argument Fallacy, and Moving the Goalposts. Anecdotal Fallacy is simple to spot but hard to discredit because it's based on opinion, not fact (i.e. a commoner in the Phoenix land states that because he's never seen an Oni, therefore Oni must not exist). It can also fall into the realm of Personal Incredulity - because the speaker finds a subject hard to believe or it unaware of how it works, it must not be true. This is usually used to debate complex subjects that require some background to understand before one can be informed enough to form an opinion. For example, an Asako alchemist has discovered that by mixing a blend of minerals he can create a potent explosive. He is laughed out of court by the argument of "how can rocks burst into flame?". Of course, in this example, he could always show them... but on the Internet we seldom have that luxury.
A Poor Argument occurs when a claim is argued badly and the opponent seizes on that to discredit the entire argument. If a Mantis courtier misspeaks in court, nearly everyone present will use that to discredit her entire position, regardless of how true or good her point was. It's easy to score political points doing this, but it doesn't change the fact that she was raising a valid point. On the Internet, this is often used when somebody misspells a word or a quotation can be removed from context to seem to be contradictory.
Moving the Goalposts is a very frustrating deliberate fallacy because it is impossible to prove anything beyond any doubt, and if you move the goalposts far enough, you can argue against anything, no matter how much factual evidence stacks up against you. A ronin is making a living scamming small villages, claiming to be a powerful Void Shugenja who is capable of reading thoughts and seeing the future. When his abilities were tested by another Shugenja, he was unable to cast even the simplest spell; his response was to shake his head sorrowfully and state that "the kami will only come if enough people have faith in them". The other Shugenja states that he has faith in the kami, just not in the ronin. The ronin responds with a regretful "and that's why they wouldn't come."
Another great Moving the Goalposts example comes from determining "success" and "failure"; let's look at an Ashigaru farm in Lion lands. Their lord has commanded them to have a successful harvest, and they bust their backs harvesting, threshing, and milling. They proudly present the fruits of their labors to their lord, more of a harvest than they'd ever produced before, and the lord sniffs at it, stating that they simply did what he expected, not anything extraordinary, so their harvest was not a success. If anything, by not doing more than expected, it was a failure. By the metric the Ashigaru had set for themselves, though, they absolutely succeeded, but their lord moved the goalposts on them. (Anyone who's ever gone through a performance review has run into that one, amirite?)
There are a lot of other logical fallacies as well (all of which I'll be happy to elaborate on), such as Appealing to Emotion (trying to manipulate the audience's emotions instead of answering the question), The Slippery Slope (if we allow X, then Y will follow!), Shifting the Burden of Proof (ever tried disproving a negative?), asking loaded questions (so, how's the maho going?), the No True Scotsman fallacy (one of my favorites), Disregarded Through Origin (Oh sure, a Unicorn would say that), The Black-or-White Fallacy (something is either this or that and there's no third option), and the Middle Ground Fallacy (I say two plus two is four; you say two plus two is six - therefore, we have to agree that two plus two is five).
So, after all of that, go out and argue! Embrace ideas that are new to you and defend your own, but be sure that you don't fall into (or fall victim to) fallacies just to win an argument. And above all, be civil, because while you might feel like yelling and screaming will get you what you want, it just makes you look like a childish little bakemono. See? An Ad Hominem attack, and we're not even arguing!