As we have seen over the last few years, both the left and the right have crackpots who believe in the utility of violence. It doesn’t help that they have virtually unlimited access to guns. But only one side has militias. There are no left-leaning versions of the Three Percenters, Oath Keepers, and Proud Boys. For now, at least.
This is a fundamental difference between the left and right that doesn’t get enough attention.