As a bisexual man, it's your duty to explain this to him. . .tell him that he's a close friend, and that you have absolutely no sexual desire for him. Explain to him that you've struggled with this ever since puberty, and that if you haven't wanted to be intimate with him in the past five years, you aren't going to start now just because you told him that you were bi. Calmly explain that it's impossible to change a gay man straight, or a straight man gay.

Finally, talk about women around him, too; mention famous women, or local girls you see out walking and find out if there's any you're both attracted to. . .tell him what you find atttractive about women, what your type is etc. Keep in mind that many people are not going to feel comfortable being around someone with a different sexuality than themselves so if none of this works? At least you tried and made yourself the better person.