When equal protection is used as justification of homosexual marriage, it opens the door for any other sort of desired marriage. Such as polygamy.
Marriage laws weren’t created by either God or state as a benefit to the couple or the two parties involved. They were created to meet the interests of God and the state.
In any event, homosexuals desiring marriage have exactly the same rights as heterosexuals desiring marriage: you can marry one adult individual of the opposite sex. The protection is equal.
They’d better permit polygamy for everyone or they will find the breeding rates among muslims with multiple wives out pacing all other groups.