(Usually happens during adolescence but continues among adult guys who have trouble getting laid, are desperate, drunk, or just willing to get whatever they can.) Which gives a new meaning to gay-straight alliances.
And it's probably the source of a lot of homophobia (particularly when homophobes believe that homosexuality is a choice, which in fact may be internalized biphobia dervied from a fear of one's own bisexuality). Most people have some degree of bisexuality (sometimes just emotional) which often goes unacknowledged or not acted upon. Women are far more open about bisexuality than men are. And probably a member of the Westboro Baptist Church. As in denial, about their homosexuality and pretending to be straight.
Here are a number of possible explanations: Okay, so some of you will automatically wonder: How can gay guys sleep with straight guys?