I think the response to this also depends on the level the particular woman feels threatened at.
If she is a person who has suffered previous domestic violence perhaps this physical interference with her child was a huge trigger.
I do wonder if the father had been waiting with a nagging toddler for some time and had less than adequate parenting skills to manage a tantrum with his waiting child so lost his temper with the woman forgetting the world at the park does not revolve around his toddler like it does in his home.

Either way the father was waaaaaaay out of line. So would a woman be, behaving in the same way, only perhaps a woman would be marginally less threatening.
I imagine if someone did something similar to me and my son I would be VERY assertive and hold the swing and model good anti-bullying behaviour for my child and the other child.
I would become quite loud and tell the person they were very rude and they need to wait and I would tell my son that the person was rude and that big people need to wait turns too.
I would also say that we all need to share so we would not be much longer.

If I felt threatened I would call the police. The man behaved in a threatening manner.