But Lynah, you are thinking all Supreme Courty, taking into account that actual 14th and 5th Amendments. Numerous federal courts have shown that to be true.
Righties, on the other hand, are thinking about what gives them the willies. Their slippery slope angle with plural marriages is just a bluff. Do you think the righties would sit still for one woman, Hispanic at that, having ten husbands? No. But the political side of that one could be fun. As long as the laws permitted all comers to have multiple partners, there's no reason they couldn't put a limit on the number of partners you could have. Or maybe they could give everyone a point limit and assigning points to non suspect classes, such as hotness. Everybody could be limited to 100 points, and hotties could be worth, say, 40. If a guy (we'll use men because it makes more sense that way) had two hotties and the others weren't keeping up with the cooking, cleaning, baby-raising, and income-earning, he could create some cap space by divorcing one hottie and marrying 4 or 5 grinders. Who's to say marriage can't be both constitutional and fun.