I've brought my Bushmaster to several ranges around here -- Iron Sights, On Target, San Gabriel Valley to name a few -- and have had few negative experiences such as described. The eyeballing that I and it get is [b]usually[/b] more of a "Hey, that's cool," thing. And I've never turned down anyone interested in giving it a try. Usually, that gets me a reciprocal offer to try whatever it is that they have. I've gotten to shoot some really cool things that way. In general, I think gun folk are the good people that way.
That's not to say that I haven't had a few "hairy eyeballs" thrown my way. But early on in my AR ownership, I may have been more paranoid about it and projecting my interpretations on the looks I was getting.
I think the theory that because we are so oppressed as a group in the PRK, we tend to be better at sticking together has some merit to it.