The Supreme Court did not redefine marriage yesterday. In fact, they said the federal government could not define it differently than the states. If a state legalized same sex marriages, then the federal government had to recognize those marriages. This sounds like a ringing victory for the 10th amendment.
Since no state has legalized polygamy, then it is a logical fallacy to say the Supreme Court opened the door to it.
They did no such thing. That door will have to be opened by a state.
And then if someone can demonstrate polygamous marriages are harmful in the aggregate, a compelling case to ban them can be made in court.
Polygamous marriages do seem to be harmful in the aggregate. They lead to the abuse of women, and carry a mathematical certainty that younger and younger females will be compelled into marriages.