Completely irrelevant when the conversation is about the relationship between the powers of the state and the protections afforded citizens who've been accused or proven guilty of crimes.

Consider whether this assertion is remotely relevant in a discussion of sexual abuse in prisons?

It seems that they are saying the prisoners apparent consent, which is being denied outright, should not be denied. If so, it would be relevant, since the entire discussion of abuse hinges on it being abuse.

This seems analogous to the manipulator thought experiment in the free will debate. Imagine a scenario such that, should you choose or intend to choose X, some advanced manipulation will kick in and force you to choose Y. But in fact you chose Y and the manipulation did not kick in. Are you responsible for choosing Y?

If you think you freely chose Y in the above scenario, it seems one can freely consent even in coercive contexts. The issue is the law adjudicating between consent and coercion in such scenarios. However, if the presumed victim is not contesting consent, I find it hard to see a problem.

It isn’t ever sexual abuse to refuse to fuck someone.

Yes, but GP's assertion is that it's sexual abuse when a third party interferes to prevent consenting individuals from participating in sexual activity.

It still isn’t sexual abuse to prevent someone from having sex with someone else either.

But it's not nearly as clear-cut as your original statement. Like, there's no story that would convince me that refusing sex with someone is somehow sexual abuse (well there is marriage, but the accepted recourse there is divorce). And, generally, preventing other consenting individuals from having sex would would fall under 'being an asshole' at worst not 'sexual abuse', but maybe there's some circumstance where the former could be elevated to the latter. My point is that the implied certainty of your statements higher than warranted.

It's not sexual abuse, but it is abuse.

What? Where did that come from?

It isn’t sexual abuse for a jailer to not fuck the people they’re jailing. Describing it as abuse because of the logic that people who are in prison can’t reasonably non-coercively consent to sex with the people who are controlling every aspect of their life doesn’t make sense in the context that it isn’t abuse to not have sex.

That's not at all what the original comment said. It said, to paraphrase, that denying teenage boys their sexual agency is itself a form of abuse. I have no idea where you even got your original idea.

There was a pretty good SSC article on kind of the same subject: https://slatestarcodex.com/2017/04/04/determining-consent/

Basic idea is, yeah it feels a very wrong and likely to cover up lots of serious abuse to say that jailers are allowed to have sex with their inmates. But if you're in custody in a same-sex facility and jailers are the only people of the opposite sex you're ever in contact with, it seems also a little wrong to effectively say you're not allowed to have any sex with anyone ever (presuming you're not homosexual of course).