When someone shows a finished quilt, there's no going back to correction for most people. I'd like to enjoy the quilt for what it is, not be distracted by "there's a mistake here, there". Those comments diminish the enjoyment of the accomplishment. It they want crtique, ask for it-privately.
In the grand scheme of things, mem are rarely abused, and usually don't point out their mistakes. Concentrating on the failures (not successes) can lead to a poor self image. Do your best and know noone is perfect.