As far as alternative sexual desires go, I am not at all a fan of categorical exclusion.
It seems so mean to tell a person, "you're interested in what? Oh, I'm sorry, there's no possible way for you to achieve sexual satisfaction. That's just wrong." When instead you might say, "well, that's tricky, but let's examine our options, and see if we can't come up with something."
Certainly, the ethical implications of certain types of sex acts are more dire than others, but I think that rather than ruling something out entirely, it might be possible to find certain approaches that work better than others - like hitting during sex. If that's a turn-on for you, you're in a tight spot.
But it would be wrong to say that noone could ever enjoy being hit during sex, or that there is something intrinsically wrong about hitting a woman for sexual satisfaction (if you're unlucky enough to be attracted to what is patronizingly stereotyped as the gentler, more vulnerable sex).
Hitting a person against their will is pretty much categorically unethical (although not always illegal), but there might be (and indeed there are) people out there who are not only willing to consent to it in a sexual context, but might even enjoy it!
Furthermore, a person who gets off on hitting needn't be categorized as a monster, as it is very possible (I would even say likely) that he doesn't go around selfishly hitting people in an antisocial manner, but actually cares about and respects other people in spite of his unusual sexual interest.
And to demonize him for that interest, and to say that there's something wrong with him for deriving enjoyment from the sort of sexual fantasies he probably likes (which many people would call "sick") would be wrong.
