Well let's just see how much "twisting" this takes.
Homosexuality is a condition contrary to the Created nature. It is therefore a state of mind, or thought. A matter of continuous or obsessive thought is how a man is in his heart.
Done.
It is because he KNEW that it was both unnatural and immoral and CHOSE to continued to pursue those thoughts rather than to focus upon doing what glorifies the Father. That makes it sin.