The Trump administration’s “zero tolerance policy” regarding undocumented immigrants entering the United States has further widened the divide among Americans on either side of the immigration debate.

In light of the policy’s continuing controversy, Harvard historian Nancy Koehn joined Boston Public Radio today to talk about how dehumanization of marginalized groups has led to violence in the past.

She called dehumanization a “dangerous, dangerous step” that affects the way people are treated, and explained how studies have shown people from different countries are viewed as being more or less "human" than one another.

“How are we going to characterize people of different zip codes and origins and all other kinds of ways?” she said. “History doesn’t repeat itself precisely but sometimes it does rhyme.”

Koehn says its important to use discretion when comparing current events to past atrocities, but she says concerns about similar dehumanization are valid.

“Is there something we want to take from history? Yes,” she said “Is that a rock solid arrow from A to B? Absolutely not.”

Nancy Koehn joins us every week. She’s the James E. Robison Chair of Business administration. Her latest book is “Forged in Crisis: the Power of Courageous Leadership in Turbulent Times.”