When President Trump tweeted on Sunday that "'Progressive' Democratic Congresswomen" — an apparent reference to Reps. Alexandria Ocasio-Cortez, Rashida Tlaib, Ilhan Omar and Ayanna Pressley, who are all women of color — should "go back" to their countries, the backlash was swift. It also sparked another conversation: What makes something racist?  

Ibram Kendi, a professor and director of the Antiracist Research and Policy Center at American University, joined "CBS This Morning" to address that question from a historical perspective and discuss whether racist actions or words make someone a racist.

Kendi explained the important historical context behind telling a person of color to go back to where they came from. 

"In the 19th century, there were many, many reformers, racial reformers who thought the way to solve the race problem, the Negro problem, was to essentially send back all free blacks [to Africa]. And that started with Thomas Jefferson, his Notes to the State of Virginia which was published in 1787, and went up to Abraham Lincoln," Kendi said.