Yup, it's scary, but frankly, I don't see a lot of haters like this. I think you can have one in some convention, but it's not the majority of the people who come to your booth ! : D
It's the only time when someone told me this. I don't really know why, maybe he applied the technique of looking you down, telling you that you're the worst, to make you fail or working harder. And also, make rivalty between you and your friends. :/
As I was on a convention, I said that I had no time for mourning. Then thought about it later, when I was in front of my drawings, and remembered the things he told me. I took some time with profesional friends to see what I can take from his mean comments and worked on it. The main problem is that it's hard to choose what's good and what's wrong when the person was really, really bad with you (like mine, the dude had a really, really big ego and talked louder than me when I wanted to say something).
But yeah, have an armour about bad comments or comic hate, whatever it is. If the comment is just mean, leave it be. If it is mean but they point out major flaws, take your time to digest it and talk with other people about it. If you have a flaw in your pacing, for example, just go and ask your comic artists friends.
It needs some guts, but it worths it.