Responding to "Homosexuality is wrong, the same way incest is wrong"

[Ravenshire]

But you look at every species on the planet, to my knowledge pretty much every animal I know of does not engage in incestual acts. There must be a physical reason for this.

Nope. Incest is nowhere near as bad as the incest taboo has made us all believe. Sure there are potential drawbacks, especially in successive generations, but it's not the freak mutation machine people think it is.

Isolate a pregnant hamster, gerbil or other rodent pet and watch a whole new colony grow and thrive from severely incestuous roots. Dog breeders often breed pups with their sire or dam to reinforce positive traits and there's a laundry list of species in the above link that choose sibling and/or close cousins to reproduce over unrelated specimens.