It seems there is a general feeling that anyone who brings their child into public, does so irresponsibly....and that's almost as offensive as undisciplined children.
I may have a child, but I've also spent the first 30 years of my life with no children. I certainly understand not wanting to be bothered by someone's screaming child while I'm trying to enjoy my evening. And I'd like to think I'm smart enough to avoid putting myself (and my child) into that situation.
I think children do what they're taught. If you expect them to be respectful, they will. If you allow them to behave badly, everyone around will suffer. Any time I've taken my child to a restaurant, theater, etc... nobody would have even known a child was there if they hadn't personally seen him.
Making broad generalizations about any one group of people is never a good idea because everyone is different, not to be defined by one single characteristic.