Sometimes things become too cliche, and folks get tired of it. Thus the NVIATWAS for Poser or SOW for Bryce, etc. Most folks let it slide, since there's a fair amount of newbies that do this since that's what's ususally what is easiest to make in the programs. But when you see more or less the same thing time after time from the same person with no development, there are some folks that turn mean about it.

As for dealing with it?

1. Grow a thicker hide. Unless someone is insulting or attacking you personally (which I believe can be considered a violation of TOS), just learn to deal with it. Knowing how to spot a troll and ignore it goes a long way when on the internet.
2. Learn from it, provided there is any useful info. Sometimes people will be harsh, but at the same time offer some valid critique. Maybe better lighting? Maybe not the same content time after time? (unless it's a series) Maybe you need to put more life into your characters? etc. Also in a few rare cases the meanness is simply misinterpretation. Someone is trying too hard to push you from the "merely good" into the "excellent" category. When an artist gets too hurt by nitpicking in those cases, it's actually the critic's plan backfiring.
3. See what the other person does (if anything). Not saying there should be any flame wars or the such, but an unwarranted volley makes for fair game. Critics who make nothing themselves usually fall under the troll category, and are pretty safe to ignore. The ones that are tough actually make good art and are the ones to watch out for. (They have the most potential to devistate your ego via comparison.) Typically such artists with big elitist egos are less common at R'osity. (They're more common at ConceptArt or CGsociety where more members have managed to break into the professional scene and are competitive about it.) These people are either jerks because they expect everyone to be at some ridiculously high standard all the time or like to stoke their egos because they believe they're so much better than everyone skills-wise. Treat them as you would the obnoxious guy with the BMW which believes he's better than you money-wise.
4. It is possible to disable comments/ratings if you feel overly sensitive to such things. I guess it's a trade-off about how fragile your feelings are vs. how much you want to know what others think of your work.

Personally, I don't get too upset about such things. Yeah, it's annoying if some folks rate something low or say it's crap. (Especially if it's something with more time put into it than just a WIP, general concept, or software experiment.) But I don't cry about it. And usually it's not the bad rating or negative comment I'm annoyed with, but rather nobody saying anything to back it up. If you think something sucks, you should be prepared to explain why. (And the same if you think it's really really good.)

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Barbequed Pixels?

Your friendly neighborhood Wings3D nut.
Also feel free to browse my freebies at ShareCG.
There might be something worth downloading.