For centuries, Christian marriage vows have included some words of this nature:
and forsaking all others,
keep only unto her / him
as long as you both shall live
Sexual attraction to a person other than one’s spouse is not a reason to act on that attraction regardless of gender. It’s not a reason to cheat, and it’s not a reason to divorce (which, under these circumstances, still amounts to adultery).
The Christian marriage vows apply whether one is attracted to a member of the opposite sex or whether one is attracted to a member of the same sex. Heterosexual adultery and homosexual adultery are equally displeasing to God and harmful to the social fabric of of the world.
From time to time, married Christian men are discovered to have had clandestine homosexual affairs. One response to this situation goes something like this:
The man’s problem is not the fact that he committed sex acts with another person while married. His problem is that he is denying his essential self. At heart, he is a homosexual male. His marriage is, and always has been, a sham. His behavior is a symptom of self-loathing. His ongoing denial of his essential nature is a sin against God (who made him that way), his wife, and the homosexual community. Only by embracing his homosexuality can he be made whole. Then, he can divorce his wife (amicably, of course) and someday marry a man with whom he is truly in love.
That’s not a quote from any one source, but I think that it is a fair summary of one point of view. The problem, as I see it, is that this whole framework is contrived and irrelevant.
Why do people experience the sexual fantasies and urges they do? My impression is that the answers are more complex and the situation more fluid than homosexual-rights arguments suggest. It’s simply presumptuous to diagnose individual marriages or personal psyches based on a political narrative.
If a wife comes to me with the complaint that her husband is attracted to another woman, my answer is never: well, his attraction to her means your marriage is a joke. He should have never married you to begin with. He should leave you and go to her. His attraction her represents his essential self.
There are a number of different ways to approach this problem, but declaring the problem to be the solution isn’t one of them.