Actions are usually sinful not thoughts
Wrong. You agree with the mentioned "exception" of adultery, which really isn't an exception at all. Lust, hatred, covetousness, selfishness, pride, vanity, etc. are all sins of the mind. While they may lead to sinful actions, they are not actions in and of themselves, yet they are still sin. Also, the vast majority of sinful actions only take place
after one has given in to certain sinful thoughts that precede them.
However, this is a heterosexual sin that involves at least one of the party involved being married. "If man lusts after a woman then he has comitted adulturey with her in his heart". Well he cant commit adulturey if he or/and the woman he's lusting after isnt married!
False. The words translated as "adultery" in the Bible refer to sexual sin in general, not the specific act that adultery has come to be known as today. Even in English, the word adultery used to be more general, and later came to refer to a more specific act. Ergo, Biblical adultery is not limited to heterosexual people, nor to married people. Lust is adultery no matter who is doing the lusting, or whom is the object of said lust.
If a mere homosexual orientation is sin (which its not as only homosexual sexual behaviour is sin not the orientation) then the same would apply to a heterosexual orientation and then it would be wrong to be heterosexual! Lol which obviously it isnt. You cant have it both ways.
Attraction is not lust. Attraction is a great and awesome gift, but lust is the perversion of our natural desires. Much as gluttony is the perversion of our desire for food. It is possible for someone to have healthy heterosexual attraction without succumbing to lust; however, one only begins having homosexual attractions after they have
already succumbed to lust.
But something like homosexuality, which harms no one, is moraly relative.
You may go around with blinders on all you like, but it's been proven time and time again that homosexuality harms everyone involved. The people directly involved are exposed to many diseases that heterosexuals almost never have to worry about. When homosexuality becomes accepted, society also suffers. You may view Europe, where such things as homosexuality are mostly accepted, as some sort of Eutopia state, but the basic statistics on depression, hopelessness, and suicide in Europe paint another picture altogether.