There was quite a bit of foolishness going on near the end of that thread. But it raises a question.
If there is a thread that people don't like, is it only necessary to get a few people to collude in derailing it to get it closed?
I would think that it would be just as easy to delete the offending comments (the ones where people are calling each other vile names) as it is to close a thread. In that case people who are having a serious discussion (as serious as can be expected in cyberspace) can continue.
But then again, I am not a mod and am not privy to what they can and can't do so I'm sure that they have their reasons for not taking that approach.
Sometimes they delete the offending post(s), sometimes they just close the thread, appears to be no rhythm or reason to it. That thread was far less derailed than many that they have let continue, so either it was the content, or, as I suspect, it depends who complains and what they want.