"The appointment of someone who gives voice to so much hate," Stevenson told Christiane Amanpour
, threatens "the kind of moral influence that this nation claims to want to have, in a world that's increasingly violent and at risk."
"I really think the moral integrity of this nation is now at risk," he added.
Bannon, in addition to serving as the Trump campaign's CEO, is executive chairman of Breitbart News, which represents the views of the "alt-right," an ideology many closely associate with white nationalism, anti-Semitism and misogyny.
In interview broadcast Sunday, Trump told CBS 60 Minutes
that his simple message for supporters who are harassing minorities is: "Stop it."
Evan McMullin, a former Republican who ran for president as an independent, declared that hypocrisy.
"Saying 'stop it' to racist attacks means little when you name white supremacist darling Steve Bannon chief strategist in the very same day," he tweeted
Stevenson, who has spent his career fighting the legacy of racial disenfranchisement, told Amanpour that for those opposed to Trump's election, protesting will not be enough.
"We've had this bad habit in America where people like to protest, they like to make a lot of noise, and then they like to go home, and wait for someone else to do something," he said. "I think we didn't do a very good job of engaging communities that were going to be at risk, who have been targeted."
Those who grew up with an African-American president, he said, "made assumptions about the character of this nation" that "have been proved false."
"With protest, there has to come activism," he added.
"We've got a lot of work to do in America to become the kind of society that we claim to be," Stevenson told CNN. "We have historic poverty, historic disenfranchisement. The tensions between communities of color and the majority are at, I think, worse than they've been in a long time."
He went on, "We've got this mass incarceration problem. One in three black male babies is expected to go to jail or prison. These kinds of conditions mean that we've all got to be more active, more tactical, more strategic, and more vocal about uplifting the issues that are our priorities."