I guess that McGrath has it about right there, but I do feel compelled to add this, in the hope that it may make perhaps one or two helpful points:

I can't help but worry a bit about people who use silly, loaded terms like "Folk Police", "Folk Nazis", and the like.  It suggests that they may perhaps not yet be grown up enough to deal with criticism, constructive or otherwise.  These are rather extreme terms, after all: how many people who have blithely used those words in this thread would really feel confident about walking up to somebody and saying to them, "You are a Nazi because you don't like the way I play the flute"?  There's always the possibility that they may have lost members of their family to realnazis.  A wee bit of tact, moderation -and a little thought about what some words actually mean- might not be such a very bad idea.  If we have sense or imagination, we learn from others who are more experienced than we; often the advice we are given will seem worthless, or will feel like condescension.  So what?  Are any of us so much more important than others that our opinions automatically count for more than theirs?  The first session I attended regularly, I made quite sure that I kept in the background (several months) until I was confident enough in my technical ability to play a tune competently.  Nobody ever gave me a hard time, because nobody ever felt threatened by me, and because when I did start to take a more "up front" part, I knew what I was doing.  I listened to the people who wanted to lay down the law; it wasn't difficult, and I learned useful things, though more about how to deal with know-alls than about technique, I have to admit.  Again, so what?  If we want to play music with other people, we have to make the effort to fit in.  We do it their way, or we gradually subvert the existing set-up until it fits what we want, or we set up something of our own.  You have to really want the music; if you do, and are prepared to give it the time, effort and humility that it requires (lots), then you will get it, regardless of what other people think.

Malcolm