I think you and Moosegirl have been fortunate in the groups you've met. I've heard that "one must jump in and chair committees, become pro-active, make the changes from within, etc." This doesn't always work, but you are so right to keep attending for all the decent folks you meet.
Most guilds are indeed open and inviting to new and (here's the catch) beginning quilters. There are some that are not. It's as simple as that. The definition of a guild is a group with specialized talents, one where a prospective member had to serve an apprenticeship in order to hone her/his skills. Guilds of years past were exclusive and wanted to keep it that way.
I remember years ago when I timidly approached the membership table for a guild. I mentioned that I was a quilter who wanted to learn new techniques. They asked me if I were a beginner, because they really did not want nor did they have the time to teach new quilters. I stared at them incredulously, unable to understand why they (or these particular women) had that attitude. I asked them "wouldn't you want to foster the love of quilting with beginners; isn't that one of the purposes of a guild?" These unfriendly ladies had such an embarrassed look that I realized I had made my point. I walked away from them, but I followed up with a letter describing this incident to the head of their guild who, of course, personally invited me to join.
As always seems to happen with me (and I believe a sign from a just God), two other guild presidents in our state went out of their way to invite me to join their groups. Sometimes, you have to stand up to the "bitch factor" and pettiness that can give a distorted picture of a group.
Just another view of what's good and bad about guilt guilds.