It's not like heterosexuals (and people of all categories) don't deal with the same thing. If you are married and fall in love with someone else, it's considered a sin by Christians (well, if you act on it anyway). In fact, it's WORSE actually, because not only do Christians frown on it, pretty much everyone one else does too (believer or not). The difference is, homosexuality is in the process of moving from "taboo" to mainstream, so there is more outward resistance.
To be fair, and apples to apples, Adultery is one of the Ten Commandments, homosexuality is not. Probably for good reason as we've already discussed; there's a shitload more adulterers than homosexuals.
On the subject of the Ten Commandments, we see many of those broken all the time by self-avowed Christians. Specifically bearing false witness, coveting, the Sabbath, honoring parents, stealing (by fraud which is still stealing).
(I) I am the Lord thy God;thou shalt have no other gods before me.
(II) Thou shalt not take the name of the Lord thy God in vain.
(III) Remember the Sabbath day, to keep it holy.
(IV) Honor thy father and thy mother.
(V) Thou shalt not kill.
(VI) Thou shalt not commit adultery.
(VII) Thou shalt not steal.
(VIII)Thou shalt not bear false witness against thy neighbor.
(IX) Thou shalt not covet thy neighbor's house.
(X) Thou shalt not covet thy neighbor's wife,nor his manservant, nor his maidservant, nor his ox, nor his ass, nor anything that is thy neighbor's