Heck no, you're not being overly sensitive! I hate this, too! I know some planes can be very crowded and it's hard to get out of your seat mid-flight but I always avoid bumping into the other seats/people as much as possible, and especially do NOT yank the seat of a person in the front. I've had people do that to me while I'm eating (lucky nothing got spilled), I've had my hair pulled, etc.

Usually I'll turn around and just smile (to acknowledge them; if they smile back or say "sorry" I know they didn't mean it but at least they're aware of what they did). I may do this once more. By the third time or so that it's happened, I have no problem turning around and saying "could you please not do that, or at least be more careful?" I'm not out to pick fights with anyone on a plane, but I agree that "common courtesy" just ain't that "common" these days! Those of us defending the "old school" of please/sorry/thanks/thank-you notes/RSVP/etc. have to keep standing up against bad behavior!