Interesting story. There is a kind of dark humor in there. I personally believe that you should be more trusting of strangers. After all the saying is, "Strangers are friends you haven't met." Even so, I agree, one cannot be too trusting of stranger, but after reading your story, your actions were a little bit too harsh don't you think?
They were a little harsh, I live in a harsh town though. It is not an uncommon ruse to ask for help and then attack someone for their wallet!
Its a tricky balance!