Why should polygamy BE ILLEGAL in the U.S. But LEGAL for two gay guys to get marry?
I’ll grant you your argument on moral terms, but I actually think it remains illegal from a practical standpoint. Marriage comes with a host of things that are designed for only one person to do. For example, your husband/wife can decide if and when you should be taken off a respirator if you’re in a coma. If two people shared that right, you could run into a lot of problems deciding (legally) who should make the decision. Ditto for things like property splitting after divorce, “partial” divorces, child custody rights, etc… You’d basically have to re-write half the laws in the country to be able to accept multiple parties in a dispute. That’s not an easy thing to do, and I doubt society would want to foot the bill for doing it.
Laws frequently do not ban things because they are bad for society, but because a politically powerful group doesn’t like them. The marriage laws are the result of a Christian majority using the power of law to impose adherence to the Biblical concept of marriage on other faiths. From a practical point of view it makes no less sense to prevent a gay woman from marrying another woman as it does to prevent a wealthy heterosexual woman from marrying multiple men. I find it interesting that the objections to plural marriage all presuppose that women must, of necessity, be the subordinate member of a marriage. I’ve known many couples where that was clearly not the case.
