First and foremost, that ship must be steered safely as it travels to its destination. Violence is not limited to war or terrorism. It comes in many forms. Violence is any harm done to someone or to a group of people. It can be caused by biological weapons, nuclear contamination, or chemical pollution.
Violence can come in the form of a bullet or a rifle butt to the head. . .
The framers wrote the Constitution knowing that America would be very different in the future. They used language that was basic and universal, so it would make sense in centuries to come. Because they understood human nature and knew we would be our own worst enemy, they made sure that the Constitution provided a legal way for us to protect ourselves, even from self-inflicted harms. They realized that danger could originate from inside our borders as well as from outside. Article IV, Section 4 both guarantees that protection and authorizes the federal government to act.