Yeah, sorry to say this happens all too often :( Some people just can't handle critisism at all. I tell you - there are many many good artists out there who could do a lot better than what they're doing at the moment. They make similar renders after another and get the same praise for each one. I'm not saying my work is super original or anything, but at least I've never privately insulted anyone who has posted critique under my works. It's because of morons like the person who called you an idiot that you're not getting constructive criticism under your images. People don't want to say anything which might upset someone because then it causes things you just described. Keep your chin up :)