Being a straight male, I have absolutely no clue what another man sees, sexually, in another man, but if that's his thing, that's his thing. Who am I to attempt to impose my thoughts and feelings onto another.
Fact is, this world is crummy, so if a person finds happiness with another, male or female, good stuff.
Generally I think marriage is a farce, but whatever someone wants to do in this regard, go for it.