So... if every parent thinks they are doing quite well (and 9% never questions their ability to raise their kids properly), who are the parents of all the kids running amok in public spaces? Who are the parents who come to school to beat the teacher who dares to question the way to raise their kids? Where do all these annoying brats come from, who seem to be able to get away with everything -- even with their mother or father standing by?
I guess it really is different when they're your own kids.
(Also, 20% of the parents is sometimes envyous of people without kids.)