Heh. I did that once (with financials, I do learn what I can before going in). It was astounding how uptight and offended the interviewer got. Pretty sure he was an outlier, but it was very satisfying. I ended it by telling him I wasn't interested, and the reaction was even more satisfying.

That's the only time I've been that intentionally rude. He really deserved it, though. And (consistent with my other comment in this thread) I'd name them, but (a) they went out of business a long time ago, and (b) I can't quite remember the name of the firm. Something "clever" ca. 2004, missing a vowel.