If marriage is defined as one man and one woman, this means No More Divorce! We aren’t saying one man at a time to one woman at a time. Divorce is just as bad as gay marriage. Both are harmful to the children. Adult children of divorce have so many problems. They have told me that.
Which is why may states don’t have divorce on demand. In NC where I live, it takes a year of separation to have a “no fault” divorce. Spousal abuse or infidelity are the only grounds I’m aware of that allow for immediate divorce.
What you fail to acknowledge, or don’t realize, is marriage falls under contract law. Love isn’t part of the equation, and the thing that makes the male/female contract unique is the biological connection (largely through children).
Gay marriage “bans” (a misnomer, btw) are simply saying that the male/male-female/female palimony contract is not the same at the male/female marriage contract. There is nothing that prevents a legal contract between two individuals.