Seriously. Do people get a kick out of making others' lives miserable? Does it give them some sort of intense euphoria? Life should be a bash-free zone. Compliments are really satisfying, especially when they come from people you barely know. When a relative stranger gives another person a compliment, that person feels wonderful because they know that that person had nothing to prove and no reputation to keep up. So please people, if you don't have anything nice to say don't say anything at all. I know that sounds terribly cliche and cheesy, but it's true. Would you want others to lower your self esteem?
Neither would I.