Funny thing is, all the guys I've known who have been wary of homosexuality have actually not been opposed to it on general principles. Once you got past all the bluster and blushes, their greatest concern seemed to be the monumentally irrational fear that gay men would spontaneously run up to them and try to sodomise them - hence, they were uncomfortable around gay men. Once I'd actually made them say that, and given them a metaphorical clip around the ear for being so damn foolish, they seemed to lighten up a bit and be more accepting. I suppose it depends in exactly what way your friend is 'prejudiced' - perhaps he's just suffering from the same irrational fear, and if he actually spends some more time around gay people, he might realise that homosexuality is just a different set of preferences, possibly with better fashion sense. =)