The tradition that is disappearing is the belief that marriage is a duty, especially for women ........ Marriage is, bit by bit, becoming more about a partnership between equals who choose each other for the purpose of love and happiness. Which means it’s becoming less about giving men control over women’s lives."Giving men control over women's lives" ... we see that in the right wing efforts to deny contraception and abortion as well. It's all of a piece.
To accept same-sex marriage is to accept this modern idea that marriage is about love and partnership, instead of about dutiful procreation and female submission. Traditional gender roles where husbands rule over wives are disintegrating and that process is definitely helped along by these new laws allowing that marriage doesn’t have to be a gendered institution at all.