[driftdiver]

“— In our legal system, you may not physically defend yourself until attacked. Threats are not sufficient to justify a violent reaction. —

That is false. The legal standard can be found in any “justified use of deadly force” statute. It is to reasonably believe there is a risk of serious injury or death.”

Not quite that simple, otherwise we should shoot at anyone driving a car.

[Cboldt]

"Reasonably believe" is about as complex as it gets. The jury gets to decide if your use of deadly force was justified, and they get to substitute their sense of "reasonable" for yours.

There is no requirement that the other person actually use force. The justification for the use of deadly force turns on the risk that a reasonable person would perceive.

A threat of force is enough, depends on the threat and many other factors.