It troubles me that this is your perception of most authors on this sight. It might be my naivete, but I've seen very few authors here, or otherwise, pompous enough to disregard a reader's comments because they feel they are the end all, be all of writing. This perception of yours is either highly exaggerated or an indication of isolated incidents that you have made the rule, and not the exception, in my opinion. I for one, have received my fair share of praise and criticism. On a number of occasions, I've missed a basic edit or went too vague on a detail, taking the reader out of the story enough to need to comment. In every single case, I've considered the suggested change and made it if I saw fit. On the occasions where I found the critique would detract from my story or style, I replied to the reader with my reasons for not making the suggested change, but only after careful consideration. I doubt anyone here presumes to be above critique, whether they always agree with it or not.
In regards to your observation regarding the social niceties of reviews, I would have to disagree with you again. Reviews on a site like this aren't meant to pin point every grammar mistake, tense issue, improper phrasing, or missed word. They are meant to encourage authors who don't have the luxury of a Times Review or to see their names on a Best Seller's list. For a GA author with enough balls to post their work, reviews, both positive and negative, are the only currency one can point to as to how their work is received. The niceties you witness are tactful bouts of praise meant to encourage, in most cases, not highlight every single flaw (and on most occasions come from fellow writers or properly raised readers who know just how much courage it takes to post something to begin with and would never dream of publicly bashing someone's hard work. My personal reason for offering review "niceties" on the occasion I find a story I like is to encourage other readers to give it a chance). For the rest, we have PMs, forum discussion boards, etc. If I saw you at a party with spinach in your teeth, I wouldn't announce it over the microphone. I'd pull you aside to the restroom and point it out kindly. I view the review system in much the same way. If you want to bash my story, or a chapter, or even just a phrase, via review, I wouldn't mind, but I feel like most readers here have the tact to send a PM instead, of which I'm more than eternally grateful. More critique will breed better stories, I agree with you on that John; respectfully, on most everything else, I have to disagree.