Teen drug bust

Two teens are busted by the cops for possession of narcotics. Their day in court rolls around and the judge says to them:
"I'd hate to throw two young men in prison for a half-dozen years for something like this. I'll give you a week to convince as many people as you can to never do drugs and I'll consider that during sentencing."

A week goes by and the teens are back in court, the judge says to the first one:
"Well how did you do?"
"I was able to convince 16 people to never do drugs."
"That's more than I expected, how did you do it?"
"I drew a diagram of two circles, one smaller than the other. I pointed to the larger one and explained that that was their brain before drugs and the smaller one was after drugs"
"Great work, I'm going to sentence you to 1000 hours of community service" Looking to the other youth he says "How did you do?"
"I was able to convince 128 people to never do drugs."
The judge is clearly surprised by this and asks him "how were you able to convince so many people to swear off drugs?"
"I used the same diagram as him."
"You used the same diagram and convinced over 100 more people to not do drugs?! How is that possible?"
"Well...it was about the time that I explained that the larger circle was their asshole after prison that everyone swore to never touch the stuff"