One key aspect to conflict resolution is to acknowledge the other side’s grievances, offer any appropriate apologies (being punched in the face and have glasses broken certainly warrants a heartfelt apology), and if necessary offer any remediation that would satisfy the other party (e.g. offering to pay for the broken glasses, and most importantly, suggesting that they spoke to their child to explain that behavior is inappropriate and unacceptable).

These parents did none of that, and just waved it off as if it’s okay for the kid to do this kind of thing “because they’re hungry”.