I agree that the way he said it was not at all conducive to discussion. I've said many times to atheists on this board that when they say things like "imaginary friend" and such, they get negative reactions because of how, not what, they said. However, in this case, we're talking about bigotry that stems from inconsistent and in turn, irrational, beliefs - the belief that what the Bible says about homosexuality is correct, but that we can just ignore what it says about slavery and other things.
If he had spoken in the same manner about Bible-based rationalizations for slavery or racism, I highly doubt people would have a problem with what he said, but for some reason, people think that Bible-based rationalizations of anti-gay bigotry ought not be criticized in the same manner. That's hypocrisy and I don't sympathize with it,