May 4 was the 50th anniversary of the Kent State Massacre, where the National Guard opened fire on Vietnam War protesters on the campus of Kent State University, killing 4 people. The authorities shooting unarmed protesting Americans was a thing that happened with ludicrous regularity in the 1960s and early 1970s. Really, for most of our history, but it was particularly intense five decades ago during the era of civil rights unrest and antiwar marches. Still, Kent State was different because of the involvement of the National Guard, because it wasn’t state police or local cops doing the shooting, but an arm of the military. President Nixon, the commander-in-chief, was the enemy that needed to be stopped.