“A lot of the people I’d consider my spiritual fathers or heroes of the faith, people I look up to, for the first time that I can remember, there are serious disagreements between them,” Adam Robles, who helps lead a small church in Rutland, Vt., told me. He signed Mr. MacArthur’s statement.

Mr. Robles, who is Puerto Rican, started a YouTube channel in 2017 “to respond to the social justice stuff,” he said. “I’ve mostly gone to multiethnic churches in my life,” he told me. But he worries that as more Christians try “to attain this supposed ideal of the multiethnic church, they end up breaking the commands of God in other ways, showing partiality.” He said that criticizing the vogue for affirmative action and multiculturalism has become so politically toxic among evangelicals that he half-jokingly calls himself part of “the Evangelical Intellectual Dark Web.”

Do conservatives like Mr. Robles actually have reason to be on the defensive? After all, white evangelicals have been paying polite attention to racial justice and claiming to celebrate diversity for decades. Their intentions may be sincere, but their actions have generally seemed shallow. “You get solutions like: We’re going to hire an African-American person on staff; we’re going to change up our worship and music style,” said Will Acuff, who trained as a pastor before cofounding Corner to Corner, a faith-based nonprofit group in Nashville. “The churches gravitate toward the simplest things you can measure and quantify.”

Yet a vanguard of Christian consultants and community activists focused on racial justice is gaining a wider hearing in white evangelical institutions than ever before. Many of them have studied history, sociology — and that academic boogeyman, critical race theory, a conceptual framework focused on the power structures that help maintain white supremacy. They combine these tools with biblical arguments to challenge white evangelical assumptions about the role of the church in the world.

Radical thinkers have found their way into the citadels of white evangelicalism. Reading the black liberation theologian James Cone helped Mr. Strickland, the theology professor, see how white theologians often ignore the structural sources of earthly suffering. In 1969, the Rev. Dr. Cone admonished “new blacks, redeemed in Christ” to “say to whites that authentic love is not ‘help,’ not giving Christmas baskets but working for political, social and economic justice, which always means a redistribution of power.”

Courses in African-American theology have been on the books at moderate evangelical seminaries since the 1970s. But it is significant that Mr. Strickland has brought a thinker like Dr. Cone into the heart of the conservative Southern Baptist Convention. Mr. Strickland spent years studying in majority-white evangelical schools, where he mastered the idiom of the Christian right. When he speaks to conservative white congregations, he is careful: “While Cone’s ideas are in play, I don’t mention him by name, because I don’t want to put unnecessary stumbling blocks in their way.” Scripture’s authority comes first. “If I’m able to demonstrate that this black man in front of them has read the Bible, I gain credit with them.”

He walked me through the argument he used when he spoke at North Greenville University, a Baptist school in Tigerville, S.C. “There was the fall, and all we do now as God’s vice regents is influenced by that fall. So if we’re sinners in need of redemption, so, too, are all the things we create, like law, policy, procedure, practice. That right there is systemic injustice,” he said. “Before they know it, they’re nodding their heads. They’re agreeing that systemic injustice and racism are a form of sin. I get in the back door by walking around the linguistic land mines that are so charged in our cultural climate.”