“Because it is the duty of civilized people to stand up to the uncivilized?”
But when that society tells you not to be armed in a manner that allows you to protect yourself and others then they are telling you NOT to intervene. They get what they ask for.
And a briefcase slammed into the side of the knee would have brought the attacker down.
People tend to regard only guns or, sometimes, knives as weapons and if they have neither they consider themselves unarmed.
They are not anymore then the man who does not have a steak is unfed.