They acted as brothers are expected to act - outraged at the mistreatment of their sister, determined to catch the guy, doing everything in their power to keep her safe.

It's arguable whether the police would/could help, and how far they'd go/have the resources to pursue the matter.

In older times, three brothers knocking on your door would be the end of it. Either total capitulation, or some kind of accident.

I feel they showed considerable restraint.