^_^;; even though there isn't a rule about this, i'm going to say it anyway: if you have something bad to say, don't say it, it hurts people's feelings, instead of telling him how bad he is, you could have spent your time correcting his mistakes like for instance: "You might want to make his head rounder, it's a bit square, and his arms could be smoothed out a bit, they're lumpy, but that can easily be fixed".
Yelling at him for his terrible work and demanding that he never goes on paint again isn't exactly critazism. I may be acting like a mod, but someone had to do it, you can't just yell at people like that, you have to have an explanation for how 'bad' their work is, otherwise it's just mean and unhelpful to him. I know you only wanted to help, but beleive me, you're only hurting his feelings.