This is something many people seem to either miss or intentionally skip. You can play strictly by the rules and still fly casual, the fact that I don't let you fix a mistake doesn't mean I'm breaking any sort of social contract, especially when we're playing at a tournament.Last night I was playing X-Wing at the LGS and I was trying out Emon with bombs and EI. I could use EI to drop a bomb after taking a Focus action. A couple times I dropped a bomb and then went to take a focus, and the guy I was playing pointed out that was doing it wrong, I can't use EI for focus. The end result was the same, focus token, bomb dropped and a stress, and he was fine with letting me do it out of order. Just pointing out that someone else may not allow it. They'd be well within their rights to not allow it, and not allowing it wouldn't make them a poor sport.
Yes it would make them a poor sport. There's a solid difference between things that actually effect the game (barrel roll -> bomb drop vs. bomb drop -> barrel roll using your EI example) and pedantically nitpicking rules minutiae for no good reason other than to WAAC.
Pointing it out, totally cool. Not allowing it, perfectly within their rights. But just because you can do something doesn't mean you should.
Not allowing someone to Focus after dropping a Bomb when equiped with EI would not make a poor sport. It may make them a stickler for the rules and I wouldn't say they are being a "good sport" but I do NOT believe that sportsmanship is either good or bad with no room in the middle for neutral play.
I certainly believe the good sport will forgive errors that could easily be backed up and repeated properly but if you're going to be a slave to the letter of the rules that would not be allowed.
When it comes to sportmanship I can also see where some levels of measurement could turn into a bone of contention.