My straight friend does this...iin?

I have a friend who is basically the biggest man whore ever. He has been with more girls than any guy I know. He is simply beast as pleasuring them and all the ladies want to sleep with him. Funny thing is, he likes to give the occasional guy a blow. I have actually accidentally witnessed him going down on a good friend of mine. I asked if he has any homosexual tendencies and he said "none at all" and seemed offended. It really confuses me, because he's def not gay. He said he likes the taste of the semen though. Is it normal for a straight guy to sometimes smoke other guys?