I got involved in a discussion on a message board that had ranged into same-sex marriage. One commenter said that her husband wishes "gays would keep their sex life in the privacy of their own bedrooms. What he finds most offensive is the militant homosexual-rights activist who screams in his face something like, 'I'm queer, I'm here, and you have to accept me!' He doesn't go around advertising his sexuality, and he doesn't want to hear about theirs either. I can agree with him on that point. Whether it's gay or straight, sex belongs in private, where it's nobody else's business, and no couple of any orientation should be bringing it out in public."
I don't think too many people, gay, straight, or somewhere in between, want to have sex in public. What non-straight people do want is the ability to walk down the street holding hands or arms-around-waists with their partner and not be subject to open hostility, or to be able to marry their partner (with all the attendant societal upsides and downsides of legal marriage), or to exchange a hug and a kiss when one picks the other up at the airport, or any of a zillion other normal interactions between adults who love each other just like any other adult human being. I don't see what's so wrong with that.
I know a lesbian couple who've been together nearly as long as my mom and my stepdad (which is to say well over 20 years), and a gay couple who've been together for nearly 20 years. Why shouldn't they be able to get married? Why shouldn't they be each other's legal next-of-kin in case of emergency?
And if you want to get Biblical, the meaning of marriage has changed SEVERAL times since the Bible was written.
12 Biblical Principles of Marriage
1. Marriage consists of one man and one or more women. (Gen 4:19, 4:23, 26:34, 28:9, 29:26-30, 30:26, 31:17, 32:22, 36:2, 36:10, 37:2, Ex. 21:10, Judges 8:30, 1 Sam 1:2, 25:43, 27:3, 30:5, 30:18, 2 Sam 2:2, 3:2-5, 1 Chron 3:1-3, 4:5, 8:8, 14:3, 2 Chron 11:21, 13:21, 24:3).
2. Nothing prevents a man from taking on concubines in addition to the wife or wives he may already have. (Gen 25:6, Judges 8:31, 2 Sam 5:13, 1 Kings 11:3, 1 Chron 3:9, 2 Chron 11:21, Dan 5:2-3).
3. A man might chose any woman he wants for his wife (Gen 6:2, Deut 21:11), provided only that she is not already another man's wife (Lev 18:14-16, Deut. 22:30) or his [half-]sister (Lev 18:11, 20:17), nor the mother (Lev 20:14) or the sister (Lev 18:18) of a woman who is already his wife. The concept of a woman giving her consent to being married is foreign to the Biblical mindset.
4. If a woman cannot be proven to be a virgin at the time of marriage, she shall be stoned. (Deut 22:13-21).
5. A rapist must marry his victim (Ex. 22:16, Deut. 22:28-29) - unless she was already a fiancee, in which case he should be put to death if he raped her in the country, but both of them killed if he raped her in town. (Deut. 22:23-27).
6. If a man dies childless, his brother must marry the widow. (Gen 38:6-10, Deut 25:5-10, Mark 12:19, Luke 20:28).
7. Women marry the man of their father's choosing. (Gen. 24:4, Josh.15:16-17, Judges 1:12-13, 12:9, 21:1, 1 Sam 17:25, 18:19, 1 Kings 2:21, 1 Chron 2:35, Jer 29:6, Dan 11:17).
8. Women are the property of their father until married, and their husband after that. (Ex. 20:17, 22:17, Deut. 22:24, Mat 22:25).
9. The value of a woman might be approximately seven years' work. (Gen 29:14-30).
10. Inter-faith marriages are prohibited. (Gen 24:3, 28:1, 28:6, Num 25:1-9, Ezra 9:12, Neh 10:30, 2 Cor 6:14).
11. Divorce is forbidden. (Deut 22:19, Matt 5:32, 19:9, Mark 10:9-12, Luke 16:18, Rom 7:2, 1 Cor 7:10-11, 7:39).
12. Better to not get married at all - although marriage is not a sin. (Matt 19:10, I Cor 7:1, 7:27-28, 7:32-34, 7:38).
How many of those rules do present-day Judeo-Christians advocate? These rules are so violently misogynistic that it defies description.
Then they need to STFU about legally defining marriage as "one man, one woman," because the Bible says so.
The only Biblical reference anyone gave me for that meme of "The Bible teaches that marriage equals one man and one woman" was this: For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh. (Gen 2:24)
Okay, yeah, that speaks of marriage as being one man and one woman, but it says nothing to the effect that "This is the way it was, is, and ever shall be."
My point being, A WHOLE LOT of what the Bible has to say about marriage not only demeans women to the status of property at best, but sounds more like the transfer of said property than the union of two people who wish to make a lifetime commitment of love. And if two people who wish to make a lifetime commitment of love just happen to have the same genitalia, who really gives a shit?
I know who: those asshats who feel like it's a personal insult and a sign of the breakdown of civilization as we know it that they have to acknowledge the humanity of anyone who doesn't fit into their WASP, hetero, cisgendered, etc. world.