It's wrong to abuse substances to get high.
Mark was prescribed medical marijuana, and his friends are asking him for some.
Mark wants to have fun with his friends.
Mark suggests that they watch YouTube videos instead since he needs the marijuana.
Mark allows his friends to use his marijuana so that they can smoke as much as they want.
Mark's friends all understand Mark's reasoning and enjoy watching the videos.
Mark's friends will want more and more marijuana to satisfy their craving.