I agree that the kid is resisting in the most normal and instinctual reaction. Think about any time a parent is dealing with a toddler in melt down mode. The toddler is resisting everything!!! and that is sort of my entire point. When an adult “resists” the police it is easy to see what is instinctual (if 5 swat officers jump you, most people will fight back in some capacity) and other forms of “resistance” are more free will based (full on gun fight is certainly resisting…probably the highest form of it really). So when the police use various levels of counter measures to handle an adult suspect/individual I will always ask what was the person doing? Was the response proportional? If the person got out of the car hands up and was gunned down by a cop…well, what the hell is wrong with this picture, right? If the person came out of the car, guns blazing; I think its rather understandable why the cop fired back no?
In this case…it is a child. The only allowable way to deal with a child who is physically resisting you beyond just letting them sit there in a sort of stale mate is to use passive restraint. shoving, hitting, or in this case body slamming a child to the ground is not acceptable in any manner.
Now…if it is your own kid, and they are throwing a tantrum…slapping them upside the head is ENTIRELY acceptable. Though, its probably not going to deescalate the situation to be sure.
ultimately, I agree entirely with your last statement. It is sort of not possible for people to not resist in some form or fashion to whatever degree. And police are supposed to have training to deal with it appropriately. I am 99.9% sure that body slamming a child is not on the approved list of “appropriate countermeasures”.