A big part of learning in this field are those not so wanted critiques, it really weeds out those who want to be better and those who think they are great without any practice at all. Modeling isn't an art but more of a science; no one is ever naturally talented at it. If he quits now because a few silly comments then it is better off for him and for everyone down the line, because he would have struggled the whole way regardless. If he keeps going, he will probably struggle, but at least he has drive to push forward when it isn't so easy.
Social Darwinism is a pretty great thing.