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).