Depends entirely on the level of physical aggression of the man. It is unacceptable for people to be acting in a physically aggressive or threatening nature in a family precinct like a playground. If it takes a visit from the police to get that point made, especially in your regular stomping ground, then that's what it takes.

ETA - context: I have in the past made a statement to Police about verbal aggression/threats made by the (drunk) next door neighbour without laying charges. I felt that there was potential for the situation to escalate in the near future, and I wanted the history to be in the system if that should happen. I got the distinct impression at the time that said neighbour flagged in their records, which reinforced the soundness of my decision. Funnily enough he has been polite & nice as pie ever since.

So, I don't think there is anything wrong in this woman asserting her & her child's right to do playgroundy things at the playground without being harassed or threatened by an aggressive adult male.