And the gun owners desperately fantasizing about finally encountering a situation that will allow them to live out their Falling Down fantasies are..? The civilized people?
If you encounter a failing justice system and your response isn't "let's fix the causes" but instead "thankfully I believe in convenient self-service executions", you aren't upholding peaceable society, and I suspect that a peaceable society isn't what you'd prefer.
I would argue the prospect of people waiting to stop them is a good deterrent, a beneficial complement to any effective justice system. When seconds count, the police are at best minutes away. For example, concealed carry is demonstrably effective in mass shooting attempts in churches, ending the threat in 6 seconds:
https://youtu.be/LflruqEMlVU?si=Q4VeYnClxPGtrI88
Consider too that there are many documented cases of the authorities being incompetent to or unwilling to stop a threat, most recently in Bondi Beach, but also in Uvalde. Maybe they’re just not coming to save you?
If you encounter a failing justice system and your response isn't "let's fix the causes" but instead "thankfully I believe in convenient self-service executions", you aren't upholding peaceable society, and I suspect that a peaceable society isn't what you'd prefer.