You asked:
>What I would very much like to understand is then why exactly would it be too difficult for you to be able to help this "whipper"/"whippee" in the sexual area?
It's not so much that I would not TRY to help them. I'd do my damnedest to. My concern is that my internal attitudes would prevent me from helping effectively. I don't know if that's true, but it may be. It doesn't necessarily have to be about S/M. I'm trying to get at the more general question of what happens when your objectivity fails, and what it will take to make it fail.
You also asked why sex is so special, and compared it to eating. Don't you think that's kind of a weak analogy? Sex ties up far more of our emotional and intellectual lives than food. Sexual infidelity is still grounds for divorce in most states; eating lunch outside of your marriage generally isn't. :)