I would have to disagree that it is not a sin until urges are acted on.
If you could read the thoughts of a man who has thoughts and urges to molest and torture children. However this man never acted on those urges. You would still consider this man one sick and depraved individual.
Absolute depravity is the human condition before God.
We are all advised not to look a woman to lust after her. But who among us hasn't?
I can't think that being tempted is a sin, as we know that Jesus was tempted even as we. And we also know that He was sinless.
So I stand by my statement. I like redheads. I can't help this attraction, not that I've tried to. And perhaps homosexuality is their burden to bear. But the acts are prohibited.