You do know that it's possible to just ignore comments about things you aren't interested in rather than demanding people to stop saying those things, right? Not only has /a/ always been a community full of perverts, but there's nothing inherently wrong with those comments especially because they're about fictional characters.
That's the issue with your kind. You see a group of people having fun in the same way they've always done, then you somehow get upset at the fact they're doing something you dislike simply because of your morals, and you demand them to stop enjoying themselves, often with an aggressive tone. If you really can't see what's wrong with that behavior, then you really should stay in family-friendly anime discussion sites instead of fucking 4chan.