I, for one, think that's a perfectly adult reaction. Adults are still allowed to be angry/offended, especially when someone just directly insults you like that.
Personally, for me it would depend on the context. If it's just one random 'u suck' type comment, I might get pissed, but mostly I'd just think it was some idiot going off. I couldn't take that seriously.
If it happens repeatedly, or worse, if the idiot in question attempts to methodically explain WHY my work is trash and what I need to do to "fix" it...they have officially awakened the beast.