Now I enjoyed Will & Grace as much as anybody, so before you start telling me I'm not "open minded," maybe keep that in mind and ask yourself who's really the closed-minded one here, hmm? Let's just move on.
With all the homosexuals and whatnots going on and on in their cute little voices about marriage, chances are that one of your family members—probably the one you've always suspected—will "come out" as a "gay," a "lesbian," or a "tran," and then insist civil unions, for some reason, "aren't good enough." As with most things in life, I've found it's easier to "be a Tootsie, Roll with the punches" than refer these tainted souls to, say, 1 Corinthians 6:9-10, because unless it's a Tweeter, they probably can't read it.
So here's my advice, and I should know, because my nephew Robert recently had a "celebration" of his "close friendship" with a fellow named "Brian." Like you, I love my family very much and want to support them—even when they make sickening decisions that will bring our family nothing but shame, misery, and disease.
I advise standing very close to the exit and not speaking any more than necessary. Politely decline any and all food or drink, as you do not know where attendees' hands have been. Loudly congratulate heterosexual couples on how happy and blessed they appear to be. When the lascivious dancing begins, do not participate in the hand gestures for the song "YMCA," I repeat: Do not participate in the hand gestures for the song "YMCA." Even if the deviants and spineless moral relativists around you begin to lift your arms and cheer "Auntie Linda," do not participate—no matter how hard you want to smile when you see that Brian fellow affectionately express his friendship with Robert, no matter how sweet it might be that these lost souls do appear to be somewhat happy, do not smile, do not dance... do not... why yes, thank you Brian, I will have some cake, and you know something, this whole "wedding" of yours is a smidge less disgusting than I thought and... oh, fuck it. WHYYYY EMMMM SSEEEEE AAAAAAYYY IT'S FUN TO STAY AT THE WHYYY EMMM SEEEEE AAAY-HAYYY!