I still ride a bike. I do 12 miles, several days a week, and as I do so I listen to music -- the Pandora service on my iPhone. I have created a station that plays folk rock. Lately, it has repeatedly played the Neil Young song "Ohio": "What if you knew her and found her dead on the ground?" On the bike, I have to repress a tear.

"Ohio" has been around for 40 years, and I have heard it over and over again. It's about the 1970 killing of four students at Kent State University during a demonstration against the Vietnam War. The killers were the equally young men of the Ohio National Guard. I was in the National Guard myself once. How did this happen? "This summer I hear the drumming. Four dead in Ohio."

The hills slow me. I grind at them, going so slowly that when the song comes on I can listen intently to the lyrics. The line about the woman dead on the ground hits with concussive force. I feel I knew her. One of the four killed was Allison Krause, and she went to school in the Washington area. Her father, Arthur Krause, sometimes called me. Arthur had devoted himself to seeking justice for his daughter. He should have known better. He was a Holocaust survivor.

Saturday, on the bike, I listened hard: "Tin soldiers and Nixon coming. We're finally on our own. This summer I hear the drumming. Four dead in Ohio."

I had been a reporter back when the killings occurred and it was a huge story to me. I longed for a chance to cover it, but I was young and raw, and the journalistic sluggers whooshed out of the newsroom, hailed a cab, jumped a plane and wrote the story -- the story. The story will keep you sane.

But it is a story no more and so, on the bike, the full horror of it came through: My God, American soldiers had shot American college students. This was not China, not Tiananmen Square, and not Iran and the pro-democracy rallies of last year -- not any of those places. This was America, just yesterday (take my word for it) and yet it had happened. How? I thought hard and then I remembered. Bullets had killed those kids, sure -- but they were fired, in a way, from the mouths of politicians.

The governor of Ohio, James Rhodes, demonized the war protesters. They were "worse than the Brownshirts and the communist element. . . . We will use whatever force necessary to drive them out of Kent."

That was the language of that time. And now it is the language of our time. It is the language of Glenn Beck, who fetishizes about liberals and calls Barack Obama a racist. It is the language of rage that fuels too much of the Tea Party and is the sum total of gubernatorial hopeful Carl Paladino's campaign message in New York. It is all this talk about "taking back America" (from whom?) and this inchoate fury at immigrants and, of course, this raw anger at Muslims, stoked by politicians such as Newt Gingrich and Rick Lazio, the latter having lost the GOP primary to Paladino for, among other things, not being sufficiently angry. "I'm going to take them out," Paladino vowed at a Tea Party rally in Ithaca, N.Y.

Back in the Vietnam War era, the left also used ugly language and resorted to violence. But the right, as is its wont, stripped the antiwar movement of its citizenship. It turned dissent into treason, which, in a way, was the worst treason of all. It made dissidents into the storied "other" who had nothing in common with the rest of us. They were not opponents; they were the enemy: Fire!

On my bike, I recalled those days and wondered if they have not returned. Sticks and stones may break bones, but words -- that singsong rebuttal notwithstanding -- can kill. We lose presidents to words and civil rights leaders to words -- homosexuals and immigrants and abortion providers, too. Richard Nixon is named in the song because he was the president at the time and because his words were ugly. He was enthralled by toughness, violence.

I hear the song more clearly now than I ever did. It is a distant sound from our not-so-distant past, but a clear warning about our future. Four dead in Ohio. Not just a song. A lesson.

cohenr@washpost.com