Last night, Hillary Clinton and her online supporters went after Bernie Sanders over his support in the 1980s for Fidel Castro and the Sandinistas. Glenn Greenwald shows why Clinton is in no position to be lecturing Sanders about tyranny in other countries. Clinton has not only walked the walk, but also talked the talk, on behalf of serial violators of human rights across the globe: Saudi Arabia, Syria, Israel, Honduras, the Gulf states, not to mention “Kissinger is a friend, and I relied on his counsel when I served as secretary of state.” As I said in a tweet last night, “Sanders stood with the Sandinistas, Clinton stands with Kissinger. Is this really a tough one?”

But Glenn raises another point worth mentioning.

Vehement opposition to Reagan’s covert wars in Central America, as well as to the sadistic and senseless embargo of Cuba, were once standard liberal positions. As my colleague Jeremy Scahill, observing the reaction of Clinton supporters during the debate, put it in a series of tweets: “The US sponsored deaths squads that massacred countless central and Latin Americans, murdered nuns and priests, assassinated an Archbishop. I bet commie Sanders was even against Reagan’s humanitarian mining of Nicaraguan waters & supported subsequent war crimes judgement vs. US. Have any of these Hillarybots heard of the Contra death squads? Or is it just that whatever Hillary says must be defended at all costs? The Hillarybots attacking Sanders over Nicaragua should be ashamed of themselves.”

In high school, I would say I was a moderate to liberal Democrat. It was an article of faith among my set that US intervention in Central America was not only strategically unwise but also morally unsound. Still reeling from Vietnam, nauseated over the barbarity of the Contras and the Salvadoran death squads, it didn’t take much in the way of liberal sympathy or imagination to think that anything the US did in Nicaragua, Guatemala, or El Salvador—short of getting the hell out of there—would be a disaster for the peoples of those nations.

Again, this was a position that was widely shared among mainstream liberals and Democrats. I just looked up the 1982 House vote on the Boland Amendment, which prohibited all military aid to the Contras, and it was 243 in favor, 171 against. Which means that some portion of moderates also adopted this anti-interventionist position.

The only reason Clinton and her supporters on Twitter can so reflexively attack Sanders over this issue—not his support for the Sandinistas or Castro, but his opposition to US intervention—is that, thanks to two decades of liberal support for regime change and humanitarian intervention, the whole discourse of liberal anti-interventionism has practically disappeared from the scene. Today, the only solid and reliable anti-interventionists you can find are either left-wing anti-imperialists, paleo- or other brands of conservative at outlets like The American Conservative, or an ever narrowing circle of IR realists like Steve Walt.

Which brings me to the millennials. I know a number of young leftists, in their 20s or early 30s, who have no experience or memory of this liberal anti-interventionism that I’ve been describing here. When they think liberal, they think of the Clintons and their allies, who are not only terrible on the issue of US power around the world, but also terrible on the question of economic justice and equality at home. They have no memory of a generation of left liberals who fought firmly for labor unions, who pushed hard for universal health care, public housing, and the like. They have no memory of a young Arthur Schlesinger rejecting Communism but nevertheless affirming that “class conflict is essential if freedom is to be preserved, because it is the only barrier against class domination.”

For liberals or leftists of my generation, or for even older liberals and leftists, the discourse of anti-liberalism on the left has a resonance. It calls to mind some of the most bruising battles of the 20th century—Communists against parliamentary socialists, Popular Fronters and Henry Wallace Progressives against the Americans for Democratic Action, Irving Howe-style socialists against the New Left, and so on. For someone like myself, who identifies with the left but who nevertheless has a great deal of respect for the tradition of liberalism, it is imperative that there be a good and productive tension between liberalism and the left.

So I can imagine when liberals and leftists of my generation, or those who are even older, hear the flat refusal of millennials on the left to even entertain the possibility of a dialogue with liberalism, it can seem scary, like a return to some of the worst moments of intra-liberal/left fratricide. But this is where history can get in the way. For the millennials, the bankruptcy of liberalism is not Walter Reuther or Hubert Humphrey or A. Phillip Randolph or Bayard Rustin; it’s Clinton, Clinton, and Clinton.

The gulf today between liberalism and the left is not of the millennials’ or even of the left’s making; it’s the product of a liberalism that has been moving right for decades and that, whatever feints to the left it has been making more recently, still has some way to go before there can be a useful and productive dialogue of difference.