Why you should appreciate constructive criticism.
last-heroine:
As an artist we experience critics sometimes on a daily basis, comments from friends, family, strangers, some are nice, some are not, some are helpful, some don't make any sense at all.
But it seems the lines blur really hard when it's about bashing and constructive criticism, so let me clear a couple of things up.
As artists (of any sort, really) we tend to be really protective of what we create, we don't like hearing bad things about it, much less some stranger telling us what's wrong with it. Why should I listen to someone who says that the clothing of my character is badly researched? Why should I listen to someone who calls my art shit? 
Do you see a difference in the questions above? Because I sure as hell do.
The first one implies my own lazyness and probably offensive portrayal of something crucial, the second one is just someone being a jackass.
And that's where you need to draw a line. 
Constructive criticism isn't there to make you feel bad about your art but to help you IMPROVE your art, it's there to point things out (in a friendly and/or polite way) and help you grow on your artistic journey. How the fuck are you supposed to improve if people only ever tell you how great and awesome you are?
I don't want to say that we are not, because artists are rad as hell but if you are an artist you also should have some ambition to improve beyond your current skill level. And if someone, regardless who, spends their time pointing things out to you and giving you a shove into the right direction, don't be an ass to them. 
Appreciate the effort they make in order to help you improve on your journey, be grateful and be polite and try to see things from different angles, these people don't want to be your enemy so don't treat them like it.
When someone offers you a helping hand, don't be an asshole to spit on it.
If you don't want your work commented on in that way THAT'S FINE TOO. Ignore the comments or say IN A POLITE WAY that you appreciate the effort but you don't seek improvement. DON'T. BE. AN. ASS. TO. PEOPLE. WHO. OFFER. HELPFUL. CRITICS.