My God tells me that I am prohibited by His Word to define sin for any other person. I am commanded to not sin, that judgement made by me, on me. Therefore, I cannot judge homosexuality as a sin. It might be a sin for me, but not for anyone else.
When Jesus told the prostitute to go and sin no more, it didn't include her running back to the brothel and calling the other girls prostitutes. Leave them be. She however was told to sin no more.
Following that advice, I would not run around telling gays they are sinful. It's not my place nor my judgment to make. My conduct is the only conduct I can judge.
It is a real shame that you cannot understand this rather simple concept. The intense personalty of the concept of sin does escape most. Even though the Bible is quite clear. Do not judge others. Over and over, do not judge others. YOU go and sin no more. Judge yourself. Take the log out of your own eye. Don't complain about the mote in someone else's eye.