I just realized there is a big age difference, your son being only 5 and this kid being 11. The age difference plus the kid's behavior would concern me a whole bunch! If you want to let your son continue this friendship, I would say they need very strict supervision at all times they are together, mainly for your son's safety!
__________________  Shannon & Puff 
"All his life he tried to be a good person. Many times, however, he failed; for after all he was only human. He wasn't a dog." Charles M. Schultz |