>How could it be consensual between all adults?

Are you trying to say multiple adults can't all agree on something? Your argument is based on ignorance and you're no better than the people who oppose gay marriage. You've been fed Christian and feminist propaganda to make you believe that only two consenting adults can love each other and that if you happen to love more than one person you shouldn't have the same rights as other people who don't.

You basically don't think polygamists are equal. Now let's see you do a full 360 from being pro-equality to using the same arguments the bigots used against you.