OK so if someone's being rude how rude do they have to be? do they have to be personally insulting? We've probably all said something at least slightly offensive to someone, but where is the line before we press that button?
Well. It's a tricky issue.
I'd have to say I follow my own guideline on the issue.
If I have not said anything rude within the thread, and the person is not contributing to their argument in any way except personal attack, then by all means, I'd push the button. I've never been in that position though, as I typically say things that attack the poster too, and few posters ever base their posts on personal attack without contributing something else to it.