Bernie Sanders is running to the left of Hillary Clinton on economic issues, but he's also attracted some criticism for keeping relatively quiet on other issues that are important to many progressives, including immigration reform. On Friday, speaking to the National Association of Latino Elected Officials, he embraced the issue — in the most Bernie way possible.

While most Democratic politicians talk about immigrants as family members of US citizens with longtime jobs and ties to their communities, Sanders focused on the exploitation of immigrants as workers.

His speech doesn't change his existing positions: Sanders supported the comprehensive reform package that cleared the Senate in 2013. And while his NALEO remarks were the first time he's addressed executive action to protect immigrants from deportation — saying he'd expand existing protections to cover parents of US citizens, legal permanent residents, and younger (already protected) unauthorized immigrants — it's in line with Clinton's position on the issue.

The reason his remarks are so interesting is that they perfectly encapsulate the Sanders school of progressivism: The biggest problem is economic inequality, and identity and social issues are simply reflections of that.

As Elise Foley reported for the Huffington Post:

[Sanders focused] on the exploitation of immigrants who "have been routinely cheated out of wages, held virtually captive by employers who have seized their documents, forced to live in unspeakably inhumane conditions and denied medical benefits for on-the-job injuries." Sanders said another of his priorities is to ensure that workers are not exploited by employers who think their undocumented status will prevent them from speaking out. He recalled a visit to Immokalee, Florida, in 2008, where he said he saw workers in tomato fields "being paid starvation wages, living in severely substandard housing and subjected to abusive labor practices."

As I've written, this is the heart of Bernie Sanders's progressivism. He believes economic inequality is not only the biggest problem facing American society, but that it's at the root of most of the other issues facing the country. It's not that he doesn't care about the particular problems faced by unauthorized immigrants, or by young African-American men threatened by police aggression. It's that he sees those as fundamentally economic problems.

When he talks about the death of Freddie Gray and subsequent protests and unrest in Baltimore, he says the "underlying issue" is the unemployment rate among young African Americans. And when he talks about immigration reform, he talks about worker exploitation.

In fact, one comment from Sanders's NALEO speech crystallizes his philosophy: "It’s time to end the politics of division, playing one group against another group — white vs. black, male vs. female, straight vs. gay, or native-born vs. immigrant." He believes progressives should protect the rights of those disenfranchised communities. But he sees social inequality as a set of symptoms and economic inequality as the disease.

Interestingly, the exception to this was the one part of Sanders's speech where he attacked Clinton on immigration — specifically, on her comments last summer that the families and unaccompanied children coming to the US from Central America should be sent back. "America has always been a haven for the oppressed; we cannot and should not shirk the historic role of the United States as a protector of people fleeing persecution," Sanders said.

Clinton has changed her tune on the children and families since last summer — she's called for the Obama administration to stop putting families in immigration detention. But by acknowledging the fear of persecution as something important in its own right, rather than framing it economically, Sanders was able to remind the audience that Clinton hasn't always been as progressive on immigration as she is today.