[nosse]

"Incest 'relationships' in the real world are mostly coercive, abusive relationships."

How do you know? Headlines tell this?

If most incest is abusive, then why we ban that non abusive incest? With the same logic you should ban all narcotics because most of them are evil (still you can buy alcohol legally).

If LGBT and straight is ok but nothing else is not, you should be able give some waterproof arguments.