I don't care enough to express an opinion on the rest of your post and the debate you're in...
I find it pretty weird that such a logical, clear thinker has no opinion on the question of whether society is unfair to approximately 50% if its members, but fair enough, your choice.
... but this part strikes me as very false. A conspiracy theory is completely unnecessary to explain the "poisoning" of the term feminism. It's entirely believable that, as radical elements of feminism naturally arose (and they did arise naturally; there's no way in hell that's a false flag operation), both non-feminists and those with actively anti-feminist inclinations lumped those radical elements with the less extreme versions of feminism. That's a story as old as time, same has happened with Islam, atheism, race relations, LGBT issues, etc. People are really bad at ignoring threatening extremes. It's a natural impulse, no deliberate poisoning necessary. As far as I know, the only viable means of fighting this trend is for the more moderate (but still similarly aligned) elements to actively, loudly disavow the radicalization of their views.
I wouldn't describe it as a conspiracy, but as a group of people attacking an idea they view as immoral or dangerous, in the most effective way possible. This often involves picking isolated sentences out of context to make a different impression that you would get reading the entire book, or blog post or whatever. Its very effective in our soundbite, 'gotcha' culture. I think the exact same thing happens to the other groups of people you mentioned, usually by the same reactionary people.
People are really bad at ignoring threatening extremes. It's a natural impulse, no deliberate poisoning necessary. As far as I know, the only viable means of fighting this trend is for the more moderate (but still similarly aligned) elements to actively, loudly disavow the radicalization of their views.
This shifts the burden from people who over-generalize to the objects of generalization, to police other people. Trying to control free thinkers and individualists is folly, as is trying to protect the ignorant from their own errors. People who are interested will explore ideas for themselves. Gay people shouldn't need to hide the guy bare-ass in chaps and a cowboy hat, and nothing else, to be respected and have equality before the law. Feminists shouldn't have to hide the bra-burners to have the same rights and opportunities as men.
I also think that for all your example there are plenty of moderates putting their ideas out there, and denouncing extremists, and it doesn't work the way you claim it should. You can't argue people out of positions they were never argued into in the first place. The majority of anti-feminists, anti-gay, anti-whatever people who I have run into have these opinions because of cultural and political identity.
Defensiveness won't get you anywhere, it'll just legitimize the suspicion surrounding the issue further.
I wasn't trying to be defensive, but to defend an idea. I didn't see any good posts defending feminism, and plenty of weak ones attacking it.