Today, almost 1,000 cities and towns in the U.S. have streets named in honor of Martin Luther King Jr., and more than 100 public schools bear his name. In Washington, D.C., a 30-foot-tall MLK memorial stands within sight of the Lincoln and Jefferson memorials. And each year, in January, we celebrate Dr. King’s birthday as a national holiday.

But in hallowing King we have hollowed out his legacy. We remember his dream of unity and justice without deeper consideration of the radical Christianity upon which that dream was built. King’s Christianity presents a challenge to liberals, who are often uncomfortable with religion in the public square, as well as to conservatives, who are more likely to embrace religion in politics but don’t align themselves with the implications of many of King’s core beliefs.

The popular version of King’s life story holds that he grew more radical in his later years—more like Malcolm X, more antagonistic to the American government in general and to materialism and militarism in particular. But that’s an oversimplification that leads us to downplay his most challenging ideas.

King adhered to the same Christian beliefs all of his adult life, views shaped by his upbringing in the Black Baptist church and the violently racist American South. If many Americans failed to notice King’s early radicalism, it was probably because they didn’t wish to see it, or were distracted by his readiness to engage respectfully with political opponents, or because his battle against Southern segregationists presented, to many observers, a clear-cut struggle between good and evil.

It should come as no surprise that a Baptist preacher with a bachelor’s degree in divinity and doctorate in systematic theology should bring religious values to his work as an activist. The surprise is the way those values pushed King to take confrontational and unpopular stances as he gained national influence, when he might have been tempted to moderate his views in order maintain popularity. Even after violent attacks, King never backed down. If anything, he grew more aggressive.