"Do you think incest and polygamy will be legalized?" - Part 4

I came across a poll on the subject of the future of full marriage equality:

I was watching a TV show recently and surprisingly, three characters (two men and a woman) got together in a sexual AND romantic relationship - as in, it wasn’t just a kink, they were serious about it, they even made their relationship official to their family/friends. And it got me thinking, do you guys think polygamy will ever be legalized? And incest? And should they be, and if not, why? Will our society ever see it as acceptable/normal like with gay relationships?

More eugenics...

This was a reply to a response I left to OrbitalResonance:

OrbitalResonance, on 28 Apr 2014 - 09:59 AM, said:

[...]

Yes, I am a fu!king Nazi. Don’t you ever use slippery slope with me you small minded buffoon. Incest is immoral while polygamy and homosexuality are acceptable. My logic is one that measures consent and consideration for the end result. There will be a line drawn.

Wasn’t saying you were in favor of those things. I’m making a point, that there’s no clear logical barrier between discriminating against one group[ of consensual adults'] reproductive rights regardless of their actual genes and behaviors, and [discriminating against] another group['s]. Some relatives could have healthy children, some wouldn’t. It depends on individual genomes, epigenomes, and lifestyles, all of which can be determined to some degree and used to make responsible decisions (which is what Israel did with the Samaritans). I think we should have free genetic screening and counseling for everyone, since it makes it easier for people to make responsible reproductive decisions.

The thing is, people who would never advocate for using state force to control people’s consensual sexual and reproductive lives will all of a sudden be okay [with it] when it comes to “incest”. It’s just because that’s the only logical sounding argument most can come up with besides “eww”. I’m saying a) it’s bad eugenic policy anyway, and b) people should be more careful suddenly becoming pro eugenics just because it serves them on one issue. After all, if we’re policing the gene pool and trying to prevent abnormal births, why aren’t we banning sex for people who are past middle age? The reason a eugenic argument allows for bad logical consequences, is because it’s being applied arbitrarily to a large group of people based on an act that’s not necessarily even reproductive. (I also don’t think eugenics is a proper role for a democratic state.)

Actually, let me quote that Slate article:

My guess is that this is how governments will manage unconventional sex practices in the next century. We can’t stop people from doing what they want to do. We’ll tell them what’s generally dangerous. And if they can adequately reduce the medical risks, by wearing a condom or taking a genetic test, we’ll look the other way. We’ll speak the language of science, or none at all.