I think it's a problem endemic in a lot of non-professional creative "industries", looking at fanartists as well as things like scanlation and the like. People are just allergic to criticism... but also sometimes it's well-founded because anonymous assholes can ruin their day.
Definitely agree with this. I've found that a lot of people in non-professional (and even professional!) creative "industries" like this either:
A. Don't know how to give critique without resorting to personal attacks.
B. Don't know how to take critique without feeling it is a personal attack.
C. Think they know everything and do not listen to anyone's critique at all, limiting their progress/improvement.
I personally think everyone should be open to constructive criticism, even if it means attracting unsavory anonymous assholes. But I know it's a tough thing sometimes, especially in today's internet scene.