When discussions turn into exercises in chucking insults around, I suspect there are two reasons. One is that chucking insults can be fun, if they are imaginative and it's done in a spirit of fun.

But when it happens in a thread about a serious issue, and it turns nasty, I think one reason is that some people have absorbed the notion that it is insincere or inauthentic to have a discussion in calm terms about an issue where you feel strongly. It's seen, I suspect, as a kind of unhealthy repression.

Best thing is to ignore that posts coloured by that assumption, and resist the temptation to respond in kind. And make a firm resuolyution never to submit a post written in anger until the next day, by which time someone else will probably have put in the boot anyway.