I think it was inspired comedy. I agree that some slapstick just doesn't work. A case in point was the movie "Home Alone". The kid inflicted horrible injuries on the two hapless burglars and I actually cringed at some of the stunts.
Yes, I remember some of the nasty things he did to Pesci and Stern. When that movie came out, the concept of actors who don't get hurt and the difference between a stunt and an actual violent act hadn't really cemented in my mind (I was 5 when it came out). I was disturbed by some of the booby traps he set up.
Slapstick in the Three Stooges vein doesn't bother me. If it looks really painful--I can't watch.