Nobody cares what you think. Once a creation has been put into the world, you have only one responsibility to its creator: Be supportive. Support is not about showing how clever you are, how observant of some flaw, how incisive in your criticism. There are other people whose job it is to guide the creation, to make it work, to make it live; either they did their job or they didn't. But that is not your problem.
If you come to my show and you see me afterward, say only this: "I loved it". It doesn't matter if that's what you really felt. What I need at that moment is to know that you care enough about me and the work I do to tell me that you loved it, not "in spite of its flaws", not "even though everyone else seems to have a problem with it", but simply, plainly, "I loved it." If you can't say that, don't come backstage, don't find me in the lobby, don't lean over the pit to see me. Just go home, and either write me a nice email or don't. Say all the catty, bitchy things you want to your friend, your neighbor, the Internet.
Maybe next week, maybe next year, maybe someday down the line, I'll be ready to hear what you have to say, but at that moment, that face-to-face moment after I have unveiled some part of my soul, however small, to you: that is the most vulnerable moment in any artist's life. If I beg you, plead with you to tell me what you ''really'' thought, what you actually, honestly, totally believed, then you must tell me "I loved it." That moment must be respected."