And people wonder why I'm a cynical misanthrope.
If you tell the kid to do something cathartic to unwind, which in this case was drawing a picture, don't punish him for following your suggestion, unless of course he actually tries to do what he drew, and if the picture was really worth that much concern, sit down with the kid and actually talk to him about it, if it turns out he has no desire to do what he drew and was just venting because he was mad then let it go.
If you tell the kid to do something cathartic to unwind, which in this case was drawing a picture, don't punish him for following your suggestion, unless of course he actually tries to do what he drew, and if the picture was really worth that much concern, sit down with the kid and actually talk to him about it, if it turns out he has no desire to do what he drew and was just venting because he was mad then let it go.