Well, what immediately leaps to mind is that I can't imagine someone coming up to you in the street and saying "you can't prove a negative, you know." It's usually offered, I would say, as a response to an attempt to discredit someone else's belief, in which case one might argue that you started it.

But aside from that, the major point that occurs to me is that, while *I* certainly regard atheism as a belief like other beliefs, and therefore worthy of respect to the same degree to which the atheist respects other beliefs, it has frequently been pointed out to me that I am wrong and that atheism is not a matter of belief but of logic. In which case, we have apples over here and oranges over there, and as far as I know there is no reason not to attempt, by means of logic (however flawed), to test a logical proposition. To get upset over that, as one might get upset at an attack on one's beliefs, is...not logical, Captain. :)