GGamer,
Have you ever actually examined the basis for believing that homosexuality is a sin?
Level of Offense:
Even assuming being gay is a sin, the punishment, and level of severity, doesn't fit the crime. There are two levels of "sin." Mortal (very serious) and Venial (not so serious). All abominations are Mortal (very serious) sins. If homosexuality is an abomination, then it is also a mortal (very serious) sin. Here, that'd be like saying jaywalking is a felony. I posit this doesn't make sense for numerous reasons including but not limited to these:
Being Voluntary?
If God is all knowing, all powerful and all loving, then he would be fair and wouldn't make people a certain way just for them to be punished for the way he made them. If you think being gay is a sin, if being gay really isn't something you can control, then it shouldn't be a sin at all. Logically, if God made everyone, including gay people, then he made them how they are. Here, if how they are means gay, then punishing them for being how he made them, doesn't add up. They didn't do anything; God did (making them gay). All the other sins you mentioned like stealing, have a thing you can avoid doing: namely stealing. God doesn't make people steal. If being gay is somehow an inborn, unchangeable trait "from God," then it can't be a sin anymore than having any other inborn, unchangeable trait. Even in criminal law, if you really can't help it/had no other choice, then you aren't guilty and you go free (reflex, another person physically moving you, automatism, duress). No "forgiveness," required.
To be fair, rules have to leave you other choices. Otherwise, they're just punishing you for the sake of punishing you and you have no option to abide by said rules, but are merely doomed to punishment no matter what. If it stands to reason that God is all knowing, all powerful and all loving, then he won't make people who, solely because of the way he made them violate rules he made. That would be unfair and he wouldn't do that, would he? Moreover, if God's labor is infallible, and God made gay people gay then saying being gay is wrong is saying God's wrong for making them gay.
Translation Issues/Rogue Authors?:
Have you ever considered the possibility that being gay isn't a sin at all? Even assuming the divine source of the Bible, maybe something got lost in translation or changed by the very mortal human, and therefore able to make mistakes, men who wrote it down? Perhaps Leviticus was incorrect to say wearing clothing of mixed threads, eating shellfish, etc was a sin and thus he may have also been incorrect to say being gay was a sin? Maybe Leviticus just decided to add his own list of stuff in there that he didn't like and ban it, which might explain why the rest of the bible, including the stuff with Jesus, doesn't mention being gay at all? Maybe God doesn't care one way or the other about being gay but only Leviticus did?
Lack of Harm:
Is harm required for something to be a sin? The other things you mentioned harm people or potentially do. Stealing deprives the owner of property. Killing is obvious. Lying can lead to all sorts of loss, etc. How exactly does homosexuality hurt anyone? I propose to you that it doesn't. If you have two consenting adults who have chosen the same sex and won't marry the opposite sex, then they're either going to be together or alone for the rest of their lives. These two people being together doesn't harm anyone and alleviates their loneliness. Even if homosexuality is a choice, then it still isn't one that would hurt anything.
Judge not lest ye be judged:
Even assuming it is a sin, whose' place would it be to punish it? No one here.... What's that about a first stone and only casting it if you haven't sinned?
At least now you've seen some of the other side....