My best friend just came out to me and I came out to him... now he wants to have sexual relations, what do I do?

It all happened a week ago. He told me he was bi, I told him that I am gay. After an awkward conversation he told me that he wanted to have sex with me minus an actual relationship and he told me that he prefers women but likes men as well. This is all troubling to me because I don't have any interest in him as a partner and telling me that he likes women is a big turn off. But the guy has never had a relationship with a man or woman. I kind of feel bad for him, he has had a lonely life. I have had several relationships both platonic and sexual. I would like to find a way to tell him that I am not his guy without hurting his feelings. We have been friends for 6 years now and the only reason why I haven't told him that I was gay before this point is because of his families very conservative views.

On a side note, What is the best way to tell girls who are infatuated with you that you are gay without offending them? For whatever reason, people have a hard time actually believing that I am gay. Thank you for your help!