Sex contrary to the traditional meaning of sex is similar to the "stolen concept" fallacy Rand talks about. It accepts some premises of the traditional sex positions (like the stuff about sex being good and important), while also contradicting a bunch of them. The result doesn't make much sense or work well.
If sex plays a traditional role in your life, I understand. If sex plays no significant role in your life, I understand. If sex plays some other role in your life ... consider what you're doing. Do you have a good reason? In general, don't actively fight with your culture over sex. Do something more productive.
Many people believe homosexuality isn't a choice. I don't know if they also believe BDSM isn't a choice. But who you have sex with, and what your ideas about sex are, actually is a choice.
Some of these choices are made in early childhood and people don't know how to change them later. People also create anger problems in early childhood and are confused about how to stop being such an angry person later in life. That doesn't make anger a non-choice. It's just a bad choice that's hard to undo later (many bad choices have lasting consequences), and it's a reasonable thing to criticize – the problems exist and have consequences, even if solutions are hard to come by. (If you don't know how to fix something entirely, one thing you can do is take steps to mitigate the damage. E.g. you can apologize for getting angry and say you think you're in the wrong. That's better than blaming other people for making you angry and denying that your anger is a flaw.)
The "homosexuality is not a choice" crowd are confused. They say it's genetic. But if it was genetic it'd be easier to change. Hair color is genetic and is changed by dye. Eye color is genetic and can be changed with colored contacts. Having a right arm is genetic, but can be changed with an axe.
What's really hard to change in life isn't genetics, it's memes. Genetics offer a limited obstacle but don't actively do anything to stop you from changing. Memes aren't set in stone at birth, like your DNA; memes can adapt as you try to change. Static memes also have much more knowledge in them than your genes.
The actual details of what to do are messy. For example, casual promiscuity could be seen as contrary to traditions of monogamous marriages, but it also has substantial cultural support today in the US, particularly for young adults. So doing that isn't fighting your culture in a direct or immediate way, though it does clash with some deeper values in our culture.
Some people are into "kinky" stuff that takes a lot of time and attention, and clashes with our culture more clearly (though there are supportive subcultures). Could they change that, and still be happy, if they wanted to and thought their lifestyle was bad? In many cases, yes. Some things are hard to change but they aren't all. Many people can make some changes if they actually want to.
Homosexuality is particularly hard to change. It unfortunately does involve fighting your culture on sex in many locations. There are lots of places where many people strongly disapprove of it and view it as extremely anti-traditional. Some parents still disown their children over it. That motivates many homosexuals try to change, but their success rate is very low. Some homosexuals are sent to reeducation camps (conversion therapy), which again has a very low success rate in addition to often being abusive. Since it's too hard to change, people should just stop being mean to it. Part of why they don't want to do that is they don't want to encourage it. Some people are homosexuals since early childhood and it's very hard to change. But some change to bisexuality or homosexuality at a later age, and many of them change back later, so that was changeable. I think some people do overly encourage that. Some people were homosexual from early childhood and only figure that out later, but some people incorrectly think they've made that discovery because their peer group does things to encourage it. There are social groups were over 50% of people are something other than "man who likes women" or "woman who likes men", and that's a cultural phenomena that's different than people becoming homosexual in early childhood.
My main point is a "pick your battles" message can be applied to sexual deviance. If you don't know how to change something and don't think you have a choice today, OK, fine (especially if it's a recognized thing that many millions of people are supportive of, like homosexuality). But there are lots of pretty optional sexual things that people could and should change or avoid. Plus, pointing out mistakes and problems has value even if they're hard to fix, and even if you have bigger problems to prioritize. I don't want people to struggle to change something, have a bunch of anguish and grief over it, have a rough time, and fail (or even succeed at a huge cost). But I do recommend people view some stuff negatively and avoid it in the first place or make reasonably easy changes to do something else. Aim to make sex not too central to your life or identity, and to not spend your life fighting about it with your society. Try to have a reasonable sex life that satisfies you and isn't a huge distraction from accomplishing other stuff.
Update 2021-07-24: I edited this post to improve it and make it nicer.