Time will tell who was right. When marriage was redefined it opened the door other relationships most would not agree to but on the basis of "discrimination" they will continue to seek changes in the laws whether it be lowering the age of consent in the the case of pediphiles or relaxing the laws in each state over incest marriages and of course polygamy. They can all use the argument of "discrimination" to have the laws changed.
Over the past couple of decades throughout the world incest laws have been challenged and today places like China, Netherlands, Spain, Israel, and Russia for a few examples all allow incest between consenting adults. The age of being considered an "adult" varies. Even here in the US, states are loosening their laws to allow first cousins to marry. And what was once consider taboo and came with it prison time, is now seen in several states as being something that may amount to a fine. By our standards pediphilla is based on age of consent. In countries throughout the world the age of consent is much lower. In fact while we were all focused on Iran and the nuclear deal, they passed a law allowing men to marry their 13-year-old adopted daughters
Iran passes marriage law allowing men to wed 13-year-old adopted daughters | Mail Online
Do a search at Wiki on "incest" to get the lowdown on how many countries have already legalized it.