Just for Devil's Advocate purposes, I think there is a very big difference between saying "Obama is a liar because..." and "Obama is a lying jackass because...".
I personally don't care one way or the other, but some people might. I see no problem with insulting politicians (we insults plenty of other people, so I don't see why politicians would be protected). The problem is that often insulting politicians and political beliefs leads to fighting between posters. It's not the "Obama is a jackass" line that's the problem. It's the poster who responds by insulting the person who said that.
Which is why I'd give a friendly to tone it down if things got out of hand. But I don't think it should be automatically warnable. It depends on the context, the severity, and the justification for the comment IMO. There's nothing wrong with being genuinely angry with a politician and insulting them as a result if you can at least present a cogent argument to justify your anger.
I mean, that's the slippery slope of all slippery slopes if we're going to start mandating that not only is flaming posters not allowed, but flaming people who aren't even members here. Are we supposed to start giving warnings to people who say Michael Jackson is a pedophile? Some may find it offensive, and it can be trolling if it's said in a memorial thread for no reason other than to rile people up, but should the opinion not even be allowed to be stated? If people say B&B are idiots, is that warnable? If you call a Voyager character ugly, aren't you also insulting the person playing the character? I don't think anyone wants to go down that road.
Just the other day I called Congressman Pete King a dingus
for complaining about the Michael Jackson media frenzy while contributing to it himself. Should that be warnable?
Those are just rhetorical questions, I know you're not personally suggesting this.