Cal, that's why I almost never tell anyone WHY I pass on them, if I decide they aren't a match. I figure that anyone who insists on knowing why is just looking for an excuse to be abusive, so I just give a polite variation on "Sorry, but I don't think we're a match. Best of luck in your search."
From what people have told me, and from what I've read on the fora for years, the single guys are really bad for that, but I've had personal experience with that unpleasantness from SFs and couples as well. Life is too short for that nonsense, and besides, wild monkey sex is too important to take seriously anyway. :)