Police will tell you that one of the most dangerous calls they get is a domestic dispute. The disputers often turn their brunt of pent-up rage and frustration onto the police when they intervene. Many well-intentioned bystanders have also ended up suffering when they have tried to step into a dispute. Proverbs 26:17 is good advice: "He who passes by and meddles in a quarrel not his own is like one who takes a dog by the ears."
An old saying is: "Those who in quarrels interpose, must often wipe a bloody nose." It is not that injustice or violence must be tolerated, but someone considering intervening ought to ask the questions: "Who should intervene?" "How should we interpose?" "What are the consequences?"