I've often heard it suggested that something along the lines of Paul's "better to marry than to burn" should justify homosexual sex acts within the context of a permanent committed exclusive partnership. The logic allegedly applied here is that not everyone is called to celibacy, in fact most aren't, and so (in spite of Christ speaking of people "born eunuchs or made so by men") this must be equally true for homosexuals. And, indeed, I have warned of the hazards of conflating anything but a vocation to celibacy with a vocation to celibacy; specifically, I've said that assuming someone with a vocation to the priesthood also has a vocation to celibacy has led to a lot of problems, as the two things are not equivalent. Therefore, it may well be true that homosexuality does not simply equal an automatic call to celibacy.
However, does that mean homosexual sex acts are ever justified? Not at all. Because beggars can't be choosers. Although I find the concept rather strange, mixed-orientation marriages are possible, valid, and some people apparently find them satisfying. As I wrote about in another post a while ago, there is a framing problematic among both liberals and conservatives that essentializes sexual orientation, to the point of saying things (on both sides) like "gays can't marry." As I pointed out, this is untrue; gays can marry members of the opposite sex like anyone else, and likewise (in places where gay marriage is legal) heterosexuals can enter into same-sex marriages civilly. There is no "orientation test" either legally or morally (talk about something impossibly subjective!) as if we are dealing with two separate species of creature with two separate standards for morality.
That is not good Christian anthropology. Different temperaments or desires do not define different goods for different people or classes of people (as the progressive narrative of liberty might believe). Because the Good should define desire rather than desire defining the Good. We are to conform our desires and passions to the objective good. But this does not mean a leveling of all diversity, nor does it mean I am suggesting anything as odious as some sort of "ex-gay" orientation-change imperative. Indeed, the Church recognizes both celibacy and marriage as valid paths to the Good (but you do have to choose one or the other!) and I've argued recently (and, apparently, quite controversially) that, although it is wrong to express it genitally, the love (though not the lust) between same-sex couples (most of such arrangements presumably involving homosexuals or bisexuals) is still real and good, and the relationships and eros abstracted from whatever immorality they may or may not contain...are still valid, and should be recognized as such by the Church without any double standard.
Indeed, the Church's teaching about homosexual sex acts existed long before consciousness of orientation was ever raised or socially constructed, and applies to everyone. It says "these acts are sinful, and these are potentially virtuous" for everyone, regardless of the state of ones passions (about which, outside disordered desire for sinful acts specifically, the Church renders no moral judgment). Any other idea involves an essentialization of homosexuals and heterosexuals into two separate species, basically. And also raises weird questions like: under that logic, could a bisexual still be obligated to pursue only the heterosexual "half" of his attractions? Of course, the evil logic of the sexual revolution is that, once you allow something for one class of people based on a plea of necessity...that essentially means it cannot be bad absolutely, and thus is okay absolutely even for those for whom it is not "necessary." I've written about this sort of argumentative bait-and-switch involving the claim of "necessity for some" to "allowed for all" before.
Now, I have to assume that, if mixed-orientation marriage is to be pursued, there would have to be complete openness and honesty about things, however. It would be unfair to the straight party if there wasn't. Still, the point is that it is possible if a sort of bare minimum sexual release is what you need.
And that's just the thing; people who try to apply the logic of Paul's statement to justify homosexual sex acts within an equivalent "marriage," are I think forgetting that what Paul says is already a concession to human weakness, and a concession based on the assumption that natural marriage is the bare minimum sort of morality, and that the open-to-life structure of the acts in such a marriage is not irrelevant morally. Applying this to homosexual sex acts in stable relationships seems to assume that the "burning" Paul primarily referred to was only fornication (or masturbation) and so this argument "begs the question" of itself by already implicitly containing the assumption that contraceptive acts (including same-sex) are not wrong (as long as they are institutionalized in something stable). But begging the question is a logical fallacy.
Paul did not say "You have a right to satisfy your lusts." This would be a huge misunderstanding of his statement. He said, to paraphrase and interpret, "It is better to be celibate, because this world is passing away. But it seems well nigh impossible for many, because sexual release is a need almost like going to the bathroom for them. Sure, it's not strictly necessary for the individual in the same way, but rather for the species as a whole, yet it's a reality that some people are just too weak to abstain entirely. Many people aren't called to total abstinence from all release, since humans are programmed with strong urges, and so if you're going to do it, you'd better at least do it within the bare-minimum moral context."
However, this is the point about "beggars can't be choosers." Paul did not say "you get to have a maximally sexually and emotionally satisfying partner in the same person, as long as you limit yourself to just one at a time." No, Paul's advice regards only a bare minimum sort of sexual release. And while this "outlet for concupiscence" notion of marriage may seem un-romantic to us today, let's remember that in the past (and indeed, in Church teaching outside the recent befuddlement of Theology of the Body) people were more down to earth, and sex was viewed in a much more functionalist way, the "expression of love" idea not having the (misguided) hegemony it does now.
So, Paul's advice to someone tempted to fornicate or sleep around would be, "Well, then you'd better take a spouse so that you can get off in a moral context, and that will at least temporarily clear such desires from your mind" (and at the end of the day, an orgasm is an orgasm, and does have the effect of silencing carnal desire for a time no matter how it is achieved.) But this would likewise be his advice to people tempted to have sex with another man's wife, with children, with prostitutes, with themselves masturbating, or with members of the same sex. Paul would have viewed all such desires as disordered lusts, and his advice was certainly not that they should be indulged but, rather, if such temptations can't be sublimated completely, then they should be dispelled through natural release with a spouse (but he never said that release would be anything other than perfunctory on the subjective level.)
That notion requires buying into an essentialism whereby not just release, but some sort of full subjective satisfaction, is a "necessity" to people, or at least to those not called to celibacy. Which (when that logic is then applied to homosexuals) requires buying into the notion that some people are called by the mere fact of their desires to neither celibacy nor heterosexual marriage, which is simply foreign to the Christian tradition (and which assumption, in this argument, constitutes begging the question.) Rather, Paul's advice was "if you really can't keep it in your pants, if you really need release, then at least do it in a marriage. It might be perfunctory, it may not satisfy all your fantasies, but at least it will provide the release to quiet the flesh for a time." He never promised that marriage would be maximally sexually or emotionally satisfying; beggars can't be choosers, he was already offering it only as a bare-minimum-morality concession to human weakness, at least natural if not the perfection found in the evangelical counsels and their full ascetic ideal. His advice was never equivalent to "You have a right to satisfy all your specific desires, as long as you domesticate them and they don't hurt anyone, if you cannot sacrifice them completely."