Having lived in Barcelona and personally witnessed someone beat the s**t out of pick pockets, I'd say it's socially acceptable. The cops just watched and didn't care.

It's also perfectly acceptable to use physical force to get the hookers to leave you alone. I learned that one quickly when I was walking back from a bar at around 3 am. One of them walked up to me, grabbed me by my junk, and proceeded to tell me the going rates for various acts of debauchery.

Fun but interesting city...