So now is your chance to get it straight. Is it or is it not pointless?
Okay. Let's start off with where we agree. I think we both agree that under current law there is a difference between having a state recognized marriage and not having one. The biggest difference deals with things that can be dealt without the state. (Medical decisions, inheritance etc). The smaller but more intractable differences deal with stuff the state shouldn't be forcing on people anyway. (Income taxes, employer bases health insurance and social security). Now if all of that went away then the difference would be in the minds of the people involved. Does it matter if you exchange wedding rings? Not really. But people do it.
If it's pointless, why do you have a problem with polygamists, incestors, beastialitors getting it? (I don't).
If it's not pointless, tell me what the point is.
Is there a middle ground? Third option? You obviously know a lot about this, is it a fair question?
Okay. This sounds like fair questions so I'll try to give fair answers. Understand with your first question I have both a personal view largely on religious views and a legal view.
Polygamy
Personal view: On your question of what problem I have with polygamists? None really. That's been around for as long as man can remember. Yeah Paul talked about a "bishop being the husband of one wife", and Jesus' pronouncement on marriage implied 1 man and 1 woman as opposed to 1 man a several women, and every patriarch recorded with multiple wives seems to have had problems because of it, but...well I'm really not sure.
Legal view: It's tricky in our modern society. Which wife gets to make medical decisions for instance. The first because she has seniority? Or the last because maybe the husband love her more? My understanding is that Islam's worked that out, but we aren't an Islamic based country. I think courts would have a hard time figuring out the correct default rules. But if people wrote their own documents (wills, powers of attorney etc) the courts wouldn't have to guess. I'm for decriminalization of polygamy rather than legal recognition. I don't think it makes sense that a man can have 4 babies mamas, but if he has a private ceremony with a preacher where he declares he's committed to 2 babies mamas he can go to prison in some states.
Incest:
Personal view: Incest? Well that's been around a long time too. (Abraham and Sarah were half siblings). Incest eventually got sanctioned under the law of Moses and Paul spoke out against it.
Legal view: Historically there's been concern about birth defects. (Of course with gay incest that's not an issue). Obviously there aren't the problems of figure out who has priority that you might have under polygamy. But then if the taboo against adult incest is erased, what happens to underage incest? Not sure where that line should be drawn.
Bestiality:
Personal view: Ick!
Legal view: People talk about the lack of ability for an animal to consent, but animals don't consent to be eaten. If you have arbitrary life and death power over something then you have arbitrary power for anything else imaginable. I wouldn't have someone arrested for it. But an animal isn't in position to decide medical decisions for its human spouse. Still if someone wants to have a private ceremony with his/her sheep then I wouldn't arrest that person. And if that person wants to draw up legal documents that kinda make sense (inheritance is the only one I can think of) fine. And someone should be able to leave his retirement account to his sheep if he desires and buy health insurance for his sheep if that's what he wants to do.
I (sincerely) hope that helps you understand my view.