Meet the aggressor where she is, without resistance, as opposed to disapproving from above; see it from her PoV; what was this about?; what led up to this? How can we proceed positively from here?
It is not that coercion is always wrong. Self-defence and the defence of others is right. Otherwise evil could win. But when we do intervene to stop one child attacking another, that is a damage limitation exercise, to try to preserve any knowledge creating going on.
Children are not born knowing right and wrong arises out of the paternalist view of children, which mistakenly holds that children learn moral knowledge through coercion, and that no one would have any interest in improving their moral knowledge unless forced to do so. But actually, coercion impedes and impairs learning, including of moral knowledge, and the vast majority of people including children are trying to do the right thing and trying to improve, including morally, and no one has perfect moral knowledge.
In your desire to become a better parent, don’t forget to have fun with your son. Enjoy life with him now, don’t wait until you reach the state of perfection you imagine a Taking Children Seriously person should have reached. Forget it—try to laugh together. Including at yourselves. Taking Children Seriously should always add to your life, not detract from it!
The idea that coercion is needed to make it possible to have creative, consent-building relationships with children is incoherent.
When a toddler hits a parent, should the parent communicate their honest reaction, whether it be showing hurt if they’ve been hurt, or any emotional response, such as feeling anger or sadness?
Protecting the victim should not involve intentionally punishing the aggressor, either physically or by even frowning at the aggressor.
When I go to other people’s houses, I try to abide by their wishes in respect of their property and so on. I try to make my visit add to their lives rather than detract from them. I try to be sensitive and (to the extent that I think they will want this) helpful in a non-intrusive way. We all want to do the right thing, including our children.
How to handle other parents expecting you to coerce their children when their children are visiting your home.
Wherever there is coercion, lies follow as certainly as night follows day. That is why, in our society, children lie all the time and the parents tell them that lying is bad and punish them for it, even though the parents themselves lie all the time too and know that it is not true that it is always wrong to lie. Not only do parents lie all the time to their children, they often punish their children for not lying.
If you are a bystander when a parent is coercing a child, you have to let the child know that you disagree with the coercion, otherwise you become part of an adult conspiracy against the child. Maybe you can make a difference for them too.
Children have to do what they themselves think is right, with no pressure whatsoever—that’s what non-coercion amounts to—but they also have a right to be told morality as best we see it.