Marriage Is Already Open to Everyone.
In the first place, no law in any state in the United States now or ever has forbidden homosexuals to marry. The law has never asked that a man prove his heterosexuality in order to marry a woman, or a woman hers in order to marry a man.
Any homosexual man who can persuade a woman to take him as her husband can avail himself of all the rights of husbandhood under the law. And, in fact, many homosexual men have done precisely that, without any legal prejudice at all.
Ditto with lesbian women. Many have married men and borne children. And while a fair number of such marriages in recent years have ended in divorce, there are many that have not.
So it is a flat lie to say that homosexuals are deprived of any civil right pertaining to marriage. To get those civil rights, all homosexuals have to do is find someone of the opposite sex willing to join them in marriage.