Just hexbear things.

Well, that's some serious genetic damage being done. I mean just look at the Hapsburgs. It's also what eventually did in the Mammoths, since the last population was too small to maintain genetic diversity and eventually were so malformed they couldn't eat (iirc).

I would hope that by making it illegal one might ask why it's illegal and form their own opinions about it.

As well, any offspring that is produced by such a coupling will have a noticeably lower quality of life. That's the part that's immoral about it to me. Not much to do with the decisions the presumably consenting adults make, but more so about the child they would create that would likely be very sick for their whole, short life.

Why are some people the way that they are