Sometimes it does, sometimes it doesn't, Doug. I think that "twat," more often than not, carries that element of stupidity. Nastiness sometimes but not invariably, as in the example I gave. All these words need to be placed on some kind of scale of increasing pejorative intent. "Plonker" is clearly much further down than "twat" but we'll have to argue the points between. And context is important too. If I called you a bastard to your face you might punch me on the nose. But in Australia you might say to your best mate "G'day, you old bastard, howya doin'!" and it would be taken as a term of endearment. In fact, I'm thinking of using that excuse here more often...