[MMaschin]

The nature of sin is selfishness. All sin is selfish and ever selfish act is sinful.

What makes homosexuality sinful is that it is rooted in sexual selfgratification. All sodomy is typically rooted in selfgratification, but it might not always be. Even most heterosexual sex one or both partners are only interested in their own physical joy. Those acts are equally sinful. I believe that some homosexual couples are capable of having non sinful sexual activity, but I think it's rare. But, i also believe most heterosexual activity is also sinful.

Is homosexuality sinful? In most cases - yes? But most times when someone condemns homosexuals of being "sinners" because of their sexual activity are being hypocritical.

[Olog-hai]

Then you’re at odds with God, who calls all of it an abomination.

On the human level, one is only hypocritical if one condemns it while engaging in it oneself.

[NKP_Vet]

Sodomites do not engage in sexual activity. They engage in perversion. Sexual activity is only capable with two members of the opposite sex.
Sodomy strikes at the root of human nature because of its perversion of the procreative impulse, without which the race will die. But in case we don’t see it, God does.

[eyedigress]

The Bible says “Be fruitful and multiply”.

Try that with a man’s ass.