Presumably by "sinful" the maker of this meme means "forbidden by the Bible," since he or she makes some claims about what the Bible says. Some of those claims are at best shaky, and some are flat-out false. But from the start there's a begged question: many people don't tie their opposition to same-sex marriage on the claim that "homosexuality is sinful," but because of various assumptions about the nature of marriage -- that it is a religious institution, for example, despite the necessity of civil marriage in American society. Many gay people agree on that point, of course, and want religious ceremonies to ratify their unions. Think of the city of San Francisco, which supplied religious officiants and dispensed blessings even to people who registered en masse for domestic partnerships. That seems a blatant violation of separation of church and state to me, and surely not all the couples involved were religious in the first place. But this is a time-honored violation, since clergy are brought in to bless state highway overpasses, and just about everything else.
So let's look at the content of this meme. The first point is that "Jesus never uttered a word about same-sex relationships." The first thing to notice is that the meme-maker is changing the subject, as will become clearer presently: the subject of the meme is "homosexuality," not "same-sex relationships." Leaving that aside for the moment, it's trivially true that Jesus in the gospels doesn't mention men boning each other. (Though not all gay Christians would agree about that. Some believe that Jesus "affirmed a gay couple," referring to the centurion whose dying slave Jesus healed. It's not certain that these men were sexually involved with each other, but it's a tribute to the high moral standards of today's Christians that they think Jesus would approve the sexual use of a slave of either sex. Some have also argued that the Ethiopian eunuch mentioned in Acts 8 was a gay man, but that's not likely.) This is what's known as an argument from silence, which is usually considered a no-no in scholarly circles. That the gospels don't report him saying anything on the subject doesn't mean he never did so; and Jesus' silence about sex between males doesn't necessarily mean he approved of it. But he never said anything about a lot of subjects, such as slavery, and the gospels do report that he took a rather dim view of sex in general. The Jesus of the gospels is not a sexual liberal: he expected his heterosexual followers to keep their libidos on a tight leash, even refraining from lustful thoughts. His stricture against divorce and remarriage was so extreme that his disciples concluded that it was better not to marry at all, though some of them already were; and he didn't disagree with them. If gay Christians want to apply those principles to themselves, more power to them, but I haven't noticed that any do. Jesus' reported silence on homosexuality, then, is not much comfort to gay Christians.
"The [Old Testament] also said it's sinful to eat shellfish, to wear clothes woven with different fabrics, and to eat pork." Trivially true, but none of these require the execution of the offender. This is a popular approach among gay Christian apologists, who usually overlook the small detail of the death penalty, which indicates that Yahweh considered sex between males a rather graver offense than eating pork. Apologists also like to confuse impurity / uncleanness with "abomination," again overlooking the fact that impurity is remedied by at most some days of isolation and then a ritual washing. (According to the Torah a woman was impure for a given period after giving birth, but no one would argue that the Bible considers childbirth sinful. I hope.) Sin in general can be atoned for with sacrifice, and it's noteworthy that atonement doesn't seem to be an option for men who have sex with other men.
The other trouble with this retort (it's not an argument) is that the proper response would be to observe the whole Torah, not to throw the whole thing out. Christians, according to the Apostle Paul (not to Jesus) are free of the Torah, or most of it, or something. Some of its standards still are binding even on Christians, including those relating to sex. (Except for divorce, which Paul agreed was mostly unacceptable.) After all, Jesus said that the greatest commandment was to love Yahweh your god with all your heart, and how better to show your love than by obeying his every wish, instead of picking and choosing at your own selfish convenience?
"The original language of the N.T. actually refers to male prostitution, molestation, and promiscuity, not committed same-sex relationships. Paul may have spoken against homosexuality, but he also said that women should be silent and never assume authority over a man." (One commenter on Facebook pointed out that Paul's requirement of silence for women referred only to worship services; he was incorrect, however, that the ban on female authority was similarly limited.) The claim that the NT "actually refers to male prostitution, molestation and promiscuity" is false. The meme-maker probably has in mind 1 Corinthians 6:9 and 1 Timothy 9:9-10, which consist of lists of sins that will keep one out of the kingdom of heaven. Some of the Greek words have been translated as referring to homosexuality, but because these words are rare and there is no real context, scholars are still not sure what they mean. To claim that they really refer to male prostitution, molestation, and promiscuity is as dishonest as to claim that they refer to "homosexuality." (I suspect that by "molestation" the writer meant "child molestation," which is still false.) And to repeat, the vital doctrine of Christian freedom from Torah is in Paul only: Jesus never says a word about it, so I suppose it can be tossed out and Christians will start keeping kosher.
By bringing in "committed same-sex relationships," I think the writer means to claim that the New Testament only condemned exploitative and abusive expressions of sexuality, not warm mature loving Christian couples. There's no reason to think so, because loving relationships between males were part of the Greco-Roman landscape in Jesus and Paul's day, celebrated in poetry and drama, and the Jewish polemic against paganism condemned them along with prostitution and "promiscuity." (See, for example, my discussion of Robin Scroggs' book on the New Testament and homosexuality, here.)
"Because God created Adam and Eve, not Adam and Steve." "That was when the earth wasn't populated. There are now 6.79 billion people. Breeding clearly isn't an issue any more!" It wasn't an issue when Yahweh forbade men to have sex with each other, either. Or, it was at least as much an issue when Paul and Jesus encouraged their followers not to marry at all. As far as I know, there's no evidence that homosexuality interferes with "breeding" anyhow.
"The Bible also defines marriage as one-man-many-woman, one man many wives and many concubines, a rapist and his victim, and conquering soldier & female prisoner of war." This being so, why are gay Christians so insistent that they don't approve of polygamy? It's a biblical value, after all, like slavery. Yet gay Christians always agree with their antigay opponents that polygamy is as yucky as marrying your first cousin. To sum up what I've written before, Christianity rejected polygamy mainly because of the influence of Roman culture (and also perhaps because of Christianity's general dislike of marriage at all: at most, one spouse).
Which brings me to the final riposte, against the declaration that gay sex is just plain disgusting. "Props for being honest. However, a whole population of people shouldn't have their families discriminated against just because you think gay sex is icky. Grow up!" "A whole population of people" is presumably courtesy of your Department of Redundancy Department; more seriously, it assumes that gay people are a discrete "population" separate from general humanity, which I think is debatable. And I've noticed that many gay and pro-gay people are opposed to polygamy and to marriage between cousins, not because they have any arguments against such families but because it's obviously gross.
Behold, the meme-maker has given you two choices: one, "Have fun living your sexist, chauvinistic, xenophobic lifestyle choice. The rest of culture will advance forward without you." The Department of Redundancy Department is still hard at work, I see. Two, "Congratulations on being part of civilized society!" To paraphrase Gandhi, civilized society would be a good idea. It would also be nice if gay Christians and their allies were any more scrupulous about fact and logic than their antigay opponents.
