Sin is anything that disturbs the Creator's plan. In that context, homosexuality is a sin because procreation is what keeps humans ongoing and that is part of the plan. I do not think anyone is going to hell for being a homosexual, i am just using it as an example. That is why murder is off limits. You should not covet your neighbors possessions or his wife because murder would begin.
I really am not qualified to talk about any of this....it is just my opinion.