He simply pointed out the pros and cons of mugging and pick pocketing, namely that mugging a target immediately screamed an attack and often let the victim get a good look at them. And if they killed the victim, they would be the next one, as Nameless wasn't going to tolerate that kind of action in his guild. He did recommend that the muggers start practicing their sneaking and acrobatics, as if they couldn't pocket, they could still try fencing, roof work, or even adventuring if they had no aptitude for the 'finer' points of thieving.