Contrary to what you may believe Nemesis, the store just converging on this man and beating the shit out of him would not result in "justice", it would result in everyone the police could detain being arrested, and your two year old son being exposed to needless, possibly traumatizing violence depending on the severity of the beating (If everyone ganged up on him then it would probably be pretty bad, because his natural instincts would kick in making him fight back that much harder, meaning they would have to then beat him harder to keep him down).
And yeah, the mother (Who is pretty ****ing hot by the way) appears to be slight of build and not at all physically imposing.
The man who touched her son on the other hand was apparently the redneck version of Brian Blessed.
She handled the situation as best as she could without being able to prepare for it.
Getting the shit beaten out of you by a huge Paul Bunyan-looking mother****er would not have been the best choice she could have made.
lol at bystander syndrome though.