Simple,
Gay marriage won’t hurt any traditional marriages. Nobody is going to say “Wait, I can marry somebody who’s the same sex as me! So long honey, have fun with the kids...”
Legalizing polygamy can hurt traditional marriage, if a husband or a wife would want to take another spouse and the current spouse refuses, the requesting spouse can file for divorce with cause and get a favorable alimony, custody and division of assets ruling.
IF the destruction of traditional marriage weren’t the ultimate goal, you might have a sliver of a point.
The institution of marriage must be protected because it is the basis of our traditional culture, it is the best environment to raise children whether the couple chooses to or not,
and this is also why the left MUST destroy it. Families are too much of an “independent unit” to allow to exist when the goal is control.
tell that to McGreevy.