@Kestrel
tl;dr: Everyone needs to learn to just be more accepting and find their niche because no style is better than the other, it's all just preferences. Live and let live.
I think you may be a little heavy on the 'dr' side of what's been said. One of the biggest problems is that people (especially antagonist PCs, and I have been guilty of this myself at times) want to push people into boxes of 'all or nothing'. IF you don't enjoy my antagonist play at the moment, it must be because you are just one of those warm and fuzzy pretty princess TSers. Warning labels are great, but most good people are not going to want to bar anyone from play; what are they supposed to do when you join in? Tell you to get lost? Get run out of the scene themselves?
Or is it okay, maybe, to ask EVERYBODY (antagonist or not) to mind their OOC manners, to not scene dominate all the time (sometimes it's helpful to go and read logs if it's a heavily logged site). Maybe it's okay to not assume that if someone ducks out or needs to take a break from someone attacking them ICly, it may be NOT because they're a pussy who only wants to go on pony rides but because they've had someone doing that in every scene they've been in and it's stressing them out and not allowing them to actually develop their PC as much or primarily only be in defensive RP. (Which is awesome, but not if that is ALL they get to do). Just like it is okay to NOT assume that people whose PCs are snarly and snappish and mean or whatever hate your play or even your PC. That deciding to white knight someone's ass and ostracize a "mean" PC OOC/IC crossover is a pretty shitty thing to do that's deep sixing a lot of awesome RP for everyone. Or that winning/losing one time doesn't mean that's all that you're good for.
It is possible to be a difficult, hard to handle, antagonist PC /without/ needing to piss all over everyone OOCly and make every scene you're ever in no matter what it is constantly revolve around you. (For that matter, it is possible to do that as a purposeful "white knight" done well PC also, you don't need to curbstomb everyone and turn it into mememememe there either). It is not cool to assume that IC antagonists are horrible people who are only there to troll people/shit all over everyone. It's also not cool to stick one's nose in the air and say that if anyone gets stressed out/doesn't want to have antagonistic play all the time, it's because they're just a perfect princess who wants everyone to love them. While there are people who fit either extreme to a tee (unfortunately) the vast majority of people do not.
Warning labels, thematic descriptions, whatever, it has nothing to do with being an OOC jackass. You can have a very antagonistic theme with players who are not jackasses. And a 'cooperative' theme dominated by jackass players. I've seen warning labels self-applied to players who were major hosebeasts using it as a excuse to be absolutely horrible and people who were very concerned with having /and providing/ fun to other players and respectful of limits (as in, I will not think you're a pussy if you choose to limit your time with me as a result, I understand my PC isn't everyone's cup of tea, not I will change my PC to suit you.). It's really the behavior, not the warnings, that makes or breaks it. And sometimes people get a little too lazy with self-awareness. It's easy to do. I will bet you that anyone who has been a MU*er for long has created problems for themselves a time or two with self-unawareness, or they're lying. 