Having been inspired by Leroy Huizenga's recent piece at First Things, titled Opposing Gay Marriage is Rational, Not Religious, I want to contribute something along that same trajectory.
Proponents of gay marriage (or, more accurately, opponents of traditional marriage) often claim that there can be no rational argument against gay "marriage". Hence, Huizenga's volley (as well as those of others such as Francis Beckwith and Robert P. George) is significant and relevant. Opponents of traditional marriage also very often lay claim to a monopoly on love and compassion on this issue. Even though they themselves may not be gay, they so deeply and intensely care for the "rights" of others that they take a stand for gay "marriage". So, not only do they have a monopoly on moral reasoning, they also have a monopoly on compassion and empathy.
But just as opponents of traditional marriage don't actually have a monopoly on reason, despite their claims, neither do they have a monopoly on loving, compassionate other-centeredness. Indeed, the group who stands to be most directly, adversely affected by gay "marriage" is gay people themselves and so it is an act of Christian charity and love to oppose gay "marriage". And, conversely, those who are adamant about their moral support of their gay brethren are actually showing flagrant disregard for their well-being.
Before I defend the claim that gays stand to lose the most in legalizing gay "marriage", and that it's an act of love toward the LGBT community to oppose it, let me first clarify that just because this is at bottom a loving act, that doesn't mean it will always be undertaken in a loving way. Sacrificially serving others is also fundamentally an act of love, but if it's done begrudgingly or with a spiteful heart then the love is lost. Similarly, if the act of opposing gay marriage is done with a haughty or selfish heart, then the loving character of the act disappears. I have no intention of defending Christians who speak the ostensible truth but fail to do so in love, because Jesus says that they are anathema (essentially). My argument is against those who say that it's not possible to speak the truth in love -- that is, those actively supporting gay marriage in the public square, while denouncing the opposition as necessarily bigoted or hateful or irrational -- because that is also an affront to God.
Those who object to my argument would undoubtedly throw anecdotes my way of un-Christian non-love that have taken place in this battle (some real and most fiction), but I'm preemptively halting any such objections because the topic at hand is the nature of the act itself, at root, which is distinct from the question of how the act is being carried out. Though I will also say that, while there are obviously many ways Christians can go about their defense of traditional marriage wrongly and unlovingly, the vast majority of wrongs that are attributed to Christians on this issue aren't actually wrongs at all. Such as standing up for their beliefs by eating at Chick Fil-A and taking pictures of it, which is a perfectly legitimate, loving action. Beckwith makes that last point most clearly and strongly, arguing that it is absolutely an act of love between brothers in Christ and completely Christ-like. But my argument (which shall now commence) goes a step further and claims that it's also an act of love toward the LGBT community itself.
It's a simple observation, but the only proper telos for human sexuality, as created by God, is within the covenant of marriage, which appears throughout the Bible as a heterosexual union at all junctures, without exception. The verses that specifically condemn homosexuality -- which many, on both sides, curiously seem to haggle over quite a bit -- are actually mostly superfluous to the debate as the positive Biblical vision of marriage -- what it is, represents, entails and means -- necessarily precludes gay "marriage" from ever being a good thing.
Of course, even among Christians -- who should all affirm the preceding paragraph without hesitation -- some will object that they only think it should be a legal right in a free society, not that they are affirming gay marriages as good. It is only the right to do whatever we want that is good! While this is a highly dubious move -- dependent as it is on a vision of The Good which Christians are under no obligation to acknowledge or recognize, and which is actually heretical -- even if we grant it for sake of argument, it still doesn't address whether the act of legalizing something which affirms someone in their sin is helpful or harmful to that person. The Christian who cleaves to this position -- who holds that gay "marriage" is an affront to God's vision of marriage, but that it should still be legal -- is in favor of society not only tolerating sin, but affirming it positively. That Christian is helping the sinner to sin, shepherding them toward death, coaxing them along the path to damnation, and claiming that it is worth the trade because, hey, at least they can affirm the secular, liberal state's understanding of "freedom" along the way. This is obviously an untenable position.
Conversely, when we use the instrument of the modern state to reflect God's Law, the law becomes a signpost to the Law, and it performs the same function as signpost. Namely: it shows us our radical fallenness and need for radical Grace. While Grace has arrived, Law is still a perpetual movement in the story of God's love, and it's our duty as expositors of that story to not leave it out in the name of some bland "tolerance". Hence, when we refuse to leave it out -- such as when we oppose gay marriage -- we are loving our neighbors to the utmost.
What about those Christians who don't believe that gay "marriage" is an affront to God's vision of marriage? They speak manifest nonsense, rubbish, and gibberish, and in so doing slander the divine. Anathematize accordingly.