IMHO, i think making rude/nasty/sarcastic comments abt pics doesn't happen a whole lot in other photography sites like pbase or flickr. it just seems to be a CS disease.
mind you, there are tons of crap photos in pbase and flickr. and there are some truly wonderful photos there too. notice that almost all the comments posted (if any) on the pics are positive ones. what does this tell you? no comments = your work is not up to scratch. yep, no need for "sucks", "trash" or whatever comments.
even the "harshest" criticisms dished out by the pros and experts in leading photography magazines when critiquing readers' submitted photos never use words like "sucks", "trash" or "crap". they are constructive, and the worst thing they will say about a photo is that it "doesn't work" for <_______> reasons.
if that is considered "sugarcoating", then i say "sugarcoating" is a good and decent thing.
how to improve one's photography then? simple. look at the good/popular photos/galleries out there and learn to be a better critic of your own photography. as photographers (regardless of skill level), it really is not that hard to tell a good photo from a bad one.
i'm all for genuine and honest criticisms, but please, have the decency to be tactful, civilised and professional about it.