So here is what it boils down to: People who don't like the idea of Canon, Female Space Marines object to the "this is how we could make them canon" posts, but as a whole don't care if you do it in the privacy of your own gaming group. The people who want Female Space Marines (henceforth "FeMarines") tend not to come here with the proposal or question "I want to house rule in FeMarines and was hoping for some feedback on an idea" but rather "This is how we can make it a terribly real nightmare for all fans of the setting!!"
So this is what I propose : All future threads on the FeMarine topic begin with a heading to the effect of "HOUSE RULE PROPOSAL" and go from there. Thus there can be no confusion about what people want and those who reply go into the thread knowing that this isn't being suggested as a canon change - merely an idea for someone's game.
Doesn't that sound reasonable?