Civil war was 150 years ago. Why would anyone be against private community militias to protect state rights?

The government is terrified that people are going to get fed up and quote on quote "try to take this country back". Because the government knows the wouldn't last. They couldn't kill citizens, and they couldn't tell the difference between citizens ans militia. So it would be like them fighting a ghost. They really want to avoid anything that has citizens gathering with weapons.