Surely this just proves there are rude people in the world, and some of these happen to be parents? Some are more lax and their children misbehave in public, some are more considerate and teach their children manners.
I have come across plenty of rude people in 8 years of living in Forest Hill, they are all around us in among the nice ones! Some are parents, some are not. Just the other week a smart young man roughly pushed my two young children out of the way to get on a bus in a busy queue.
There aren't often threads about rude smart young men though - there seems to be particular ire set aside for mothers (people don't seem to get so hot under the collar about fathers being out and about in public and sometimes having misbehaving children).