Thats just the thing. It IS natural. Its happened since the beginning of time..read some Greek history thats not been watered down. Christianity has just destroyed as much knowledge of it as they could and has painted it "unnatural." So its been something thats been hidden, surpressed, and ignored as much as possible.
Its not just humans either. Homosexuality happens naturally in nature. Its been scientifically proven. I wonder if they ever thought it could be evolutions way of population control.