Polygamy is incompatible with our marriage laws. As you've already admitted. And that incompatibility would establish a valid justification for not incorporating polygamy.
Same sex marriage has been compatible with 2 person marriage from the moment we recognized men and women as equal partners. The second that happened....same sex marriage was inevitable. As it resolved the only incompatibility between same sex marriage and hetero marriage.
I know, for a minute there I almost thought Skylar was the attorney for the traditional marriage people at the SCOTUS Hearing this last Spring! Gee Skylar, that reverse of position took you what, like 18 hours to accomplish after last Friday's insane and unworkable Ruling (Hobby Lobby freight train coming its way..)?
Here's Skylar's "solid legal position"...>> man/woman father/mother marriage <
But on just two people being married, suddenly we have an 18th Century prude on our hands >

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And that's what you call a hypocritical bigot who was never about true marriage equality from day one. He was about promoting a cult instead that as yet doesn't want to advertise the "P" component because it migh spook the straights..and get this thing overturned..