The way you criticize the person is very important I believe, if you go like this "Your works scks you lousy stoopid f*er, that hand shouldn'T be like this you moron" etc. Its not gonna help at all, cuz all you mainly do, is your degrading the person, and that person might be so pssed at you, all he will remember is your name and not your criticism. People should suggest something, and if possible give some reference to show is point.