Countries and States vary as to what level of physical discipline is acceptable. A slap to alert a child is different that hitting a child with a rod because they spoke at the meeting, such as I used to receive at home. It is difficult to specify or agree on exactly what that limit should be.
getting hit by a car.
This is an interesting example. A parent will act instinctively to protect their young child. When my son would run towards the road, I would grab him, and then explain what could happen. As young as 2 or 3 he understood the road was dangerous. He had seen dead birds and mice and comprehended that the same could happen to him. At that age I still needed to watch him, as kids are easily distracted, but he never intentionally ran onto the road as he comprehended the consequences.
My friend on the other hand has a son the same age that would run onto the road. She would grab and hit him. His reaction was to immediately run to the road again, possibly in defiance of how he was treated. Her screams that he will get run over, threats and physical abuse taught him nothing about the danger of the road. This same mother advocated strongly against domestic violence, as she had been with a violent partner.
I took away two points from this. Firstly, if a person is against violence towards adult family members, how can they justify violence towards children? Secondly, hitting a child teaches little, and a child may end up rebelling against the treatment rather than learning from it.
A child that learns not to do something to avoid a beating is similar to a child taught not to do something because Jehovah doesn't like it. They don't learn anything productive, and at some point need an educated reason for avoiding certain behaviour. A beating followed by a discussion on why they got a beating may teach a child why something is wrong, but I have found that the discussion on its own to be just as effective. A child can be motivated to behave out of love of a parent more effectively than one that behaves out of fear.
There is far too much violence in the world, and teaching a child that hitting someone is the easiest way to control them perpetuates that cycle.