Do you think the federal government should have been forced to recognize polygamy as legal marriage?
I think it's inevitable. And not because of why you think.
Our current tax code penalizes people for being married and married people pay higher taxes. Therefore the Federal government will legalize polygamous marriages because then they can tax the income of five people earning $100,000 each at the combined rate of one person earning $500,000.
As soon as the IRS figures this out polygamy will be legal and the Democrats (and some Republicans) will vote for it.