Tell him he is a douche who can't wrap his head around acceptance, and the fact that its the 21st century, and that stuff like gay people are normal. It would suck if they were heterophobic. Imagine that...

Well then you have a prejudice against homophobes, so you too would be a douche. He has every right to dislike the idea of homosexuality. Its only when he actually seeks to harm gays based on his beliefs that he would be in the wrong. Its perfectly fine in my mind to dislike homosexuals.