Violence is justified when you have no other means left to defend yourself or someone else otherwise.

At which point I would like to add that people will sometimes not be able to see the means they have left because they are put in a stressful situation in a second. I feel like you can’t really blame them for that.

Violence as a response should always be in proportion. That should avoid escalation. In an ideal world.

Unfortunately some people won’t stop. Those people need to be put into prison where they cannot hurt anyone anymore.