In the Gay to Straight? post, I made this reply:

Arguments against homosexuality which use comparisons are often shot down because the anti-homophobic viewpoint deems the comparison unequal. For example: homosexuality-murder (not hurting anyone), homosexuality-bestiality (not consensual, for starters), homosexuality-pedophilia (not consenting adults, power relation).

What about incest? As acceptance of homosexuality as natural increases, I always wonder, will the day come when people say "If I want to have sex with my sister, that's my personal choice. What I do in the bedroom is nobody's business."

So... gay people and non-gay people who feel offended by this comparison...

Is incest wrong?
Is it a personal choice?
Is it natural?

If yes (to all 3 questions), thank you for your time.
If no (to any)...

How is homosexuality different?
How is it different in a way that makes incest wrong/unnatural, but homosexuality OK?