Common sense is another of those rarities. So rare its a super power. I agree with you on logic being one of them as well.

Though I am curious, some of the political circles I'm in occasionally come up with the argument, it's ok for gays to marry, polygamy and polyandry are ok, but what about cousin's marrying? what about brothers and sisters? what about people who want to marry animals? or inanimate objects? Should all of those be allowed too?

I'm of the opinion whatever floats your boat as long as other humans are involved. Just keep the fed-gov out of it. Though it's kind of hard to get a chicken, or a pillow to sign a contract. That's where I personally draw the line. There are some people that share a majority of my political views that think people should be able to marry chickens and/or pillows if they wish.

I was curious where you draw the line?