Why on earth is "teabagger" offensive?

I can understand that "towelhead" or "honkie" are unacceptable, as being racist, while "Bushites", and "Democraps" contain faeces-related words - but what's wrong with teabags?

Just because it sounds a bit silly is surely no ground for complaining. Is the suggestion that there's a duty not to poke fun at political opponents?

That really would be, to use a very much over-used expression, political correctness gone mad.