Did your friend go to rehab for marijuana? Or something a little more severe?

You see, if it was for marijuana, yes, they obviously filled his head with B.S., but if was there for lets say crack or meth, that I can understand. Crack and meth grab a hold onto you so hard, that any other use of substance could easily send them into relapse, eg. marijuana.

Let him talk, get some new friends, be happy he's living a clean life.