I hear ya - I'm actually considering getting a GAC in case I need it, as I get very nervous and increasingly anxious in crowds sometimes. It doesn't happen ALL the time, but if it does happen I would be knocking people over in an attempt to run, screaming, out of the line and straight for the bathroom. I did "ok" on our last trip, but we did have to leave the line a couple of times. I hate it; it makes everything I do just a *little* harder - shopping, driving, traveling. I really don't care if people don't like me having a GAC - I love Disney, and I want to feel comfortable there (unlike all the other places where I just have to suffer).
Also, I am not opposed to turning around if someone is breathing down my neck and saying "excuse me, could you give me some personal space?" That's one of the reasons I usually need to travel with someone else - I need a buffer. I can create a buffer in front of me by simply slowing down and not standing close to the person in front of me - but it's the neck-breathers that drive me crazy sometimes!
So get the card, and screw the naysayers. That's my take.