I actually bailed on myself as well after reading some of the original intentions of the law to see what it means. I do think it is meant to strike down laws that give protections to one group vs another but on the other hand my other OP could be correct still. I hope someone pulls up some originalist quotes of what the authors intended for the law to do. That would help out a lot.
Specifically, the Fourteenth Amendment was about defining what a citizen was, and to keep laws from being passed which essentially denied citizenship to people who met the criteria laid out in this amendment for citizenship. Its purpose, along with the Fifteenth Amendment, passed two years later, was to protect black people from laws designed to deny them their citizenship.
State-sanctioned marriage is not a right of citizenship, since our government also recognizes the marriages of people who are not US citizens, while they are in this country. All it requires is that they meet the criteria laid out for a state-sanctioned marriage.