I guess I have a different view than most people. I'm almost finished with classes for my masters in education, and one of the very first lessons we learned was "accept reality." Once I applied this to everyday stressful/frustrating/annoying situations in my life (not just the classroom), I became a much happier, easy going person. So Mr. Jones thinks that my class is a waste of time, and his son shouldn't haveto do the work (I teach music)... okay, I accept that and I can't change it, so I'm not going to argue, plead, or get angry when the kid refuses to do his homework. My mother-in-law is habitually 45 minutes late to EVERYTHING... I accept that, I can't change it, so now I just tell her to meet me 45 minutes earlier than I really want to (or bide my time with knitting for an extra 45 minutes).
SO, regarding this situation, IMHO it's not worth an argument, reverse psychology, or get-back-at-him tactics. Let him play with your needles; what's the worse than can happen? Yes back scratching with needles is gross... you could try buying him a back scratcher, scratching his back for him, or a million other things, but the easiest thing might just be to accept the reality that he is going to do it, and keep a rag in with your needles and wipe them off before you use them.
**end of soapbox**