I’ve made this very same argument with my more liberal friends and they also toss up the “incest” canard. Frankly, I hope to see this “loophole” exploited everywhere homo-”marriage” is legal.
Everybody assumes incorrectly that marriage between close relatives and sexual relations between close relatives are the same thing. They are two seperate issues. Two relatives who marry, hypothetically for now, may never lay a hand on each other, the purpose of the marriage was for estate planning only.