You are a human

any proof?

"sex is icky!"

lol. Seriously, though, Xapy, I'm pretty sure you would be violating the ToS if you were to pursue the 'rapist' smear. There *is* such a thing as actual defamation.

Also, Tabby, retaliating in kind can end up becoming a 'two wrongs don't make a right' situation. (Although some of the articles I've linked to recently describe 'tit for tat' as a successful strategy, it's not as simple as it sounds on the surface.)

Don't say tit! tabbster will get grossed out!

^^I don't actually want to accuse anyone. What I want to do is to force my opponent to stop his/her smearing.

In a normal case, you could reason it out with the person. In this case, he's just trolling, so either downvote or report it (if it's serious enough). Just stop feeding the trolls with your replies, though. Everyone else knows it's trolling, and they don't take such spurious accusations seriously; there's no need to reply, it just eggs them on. It 'feeds' them. Stop feeding them. (Again, if it's serious enough, then you can of course report the comment; that's far more effective than arguing with (i.e. feeding) the trolls.)