After getting a good look at this guy I'm surprised he stopped the slapping of the child, not a bay at two BTW, and give the mother a few in the bargain. This guy looks like that's his answer for everything that bugs him in life. The comment to the mother about controling her child may have been valid, but as stern as my beliefs on children are, just reaching out and smacking someone else's kid in publick is way out of line.
As for the mother, few things are more pitifull than watching a grown woman lose an argument to a 2-3 year old in the middle of a store. I can't imagine ever trying a stunt like that with my Mom- the wrath of God would be waiting for me when we got home. Parents are supposed to be raising the child to be a functional part of society, they can become friends once the kid is out of the house and on their own.