I think that people who do not have children, expect children to be "well behaved" and perfect all of the time...
I'm not going to even be humble about it...my children are STELLAR, one of the best complements I was ever paid was that my husband and I are the kind of parents that should have lots of children because of the way we are raising them....but even MY children have their moments, they have been few and far between...but it has happened....
If someone feels they can judge my parenting skills or my children for that matter on one of those moments, I could really care less..because they obvoiusly don't know me or my children. So I wouldn't judge another that way either...but I'm blessed enough to be a parent!
I also expose my children to everything from fine dining to first class, how will they learn how to behave in different environments if they aren't exposed?
The other thing I have learned as an adult is you have absolutely no idea what another person is going thru that moment or that day that may have preceeded a melt down or whatever you want to call it....so be the bigger person and keep it moving...all of that turning around and glaring does what exactly? If I'm in the middle of trying to rein in a child, the absolute last thing I need from an absolute stranger is a glare