I understand my limitations. I'm not a big tough guy. I wasn't a big tough guy when I was young. I'm less of a big tough guy at 50. And my primary sense of humanity and responsibility is toward my wife, who I can't provide for and protect if I get beat to death in a gutter.It's not chest beating. It's called humanity and a sense of responsibility.
Some of us have a conscience, and can't cowardly walk by to preserve our own safety while others are victimized.
I'm not saying that I would never intervene. I am saying that getting involved physically would not be my default response, particularly in the Boston area where I could likely get a cop (or several) there in just a couple minutes.
I have seen domestics, specifically the lamp throwing invitational at Arizona Terrace in Arlington, back around 1991. I called the police, they arrived within minutes, and the champion lamp thrower was given the silver bracelet award, with a lot less drama and violence than if I'd imposed myself into the situation.