George Bush Senior sent a letter to the writers of the Simpsons, after he saw the episode where he moves into the house across from Homer. He described it as,'the stupidest thing I've ever seen'. To which the writers replied,'Have you seen your kid?'
really dumb but what are they going to say back to that?
I would love to, but you're girlfriend already does it for me. Such a nice girl.
This will more than likely start a fight, but it's the best one I could come up with. Using the their girlfriend's real name would really hit them hard.
Remembered another great one. When Australia were playing a test match against the West Indies (cricket), as the opening Jamaican batsman was walking up to the crease, the ozzie wicket keeper asked him,'Why are you so fat?', to which the batsman replied,'because every time I f*** your wife she gives me a biscuit'. Absolutely demolished.
As far as Churchill goes, nothing beats this legendary riposte in the House of Commons:
Bessie Braddock: Winston, you are drunk, and what's more, you are disgustingly drunk.
Churchill: Bessie, my dear, you are ugly, and what's more, you are disgustingly ugly. But tommorow I shall be sober, and you will still be disgustingly ugly.
This was the first comeback that came to mind when I saw the title of this thread.