Ben Carson speaks at a luncheon during the Republican National Committee's "Building on Success" meeting in San Diego on Jan. 15, 2015. (Earnie Grafton/Reuters)

Ben Carson called out his fellow Republican presidential candidates for their reluctance to call the South Carolina church shootings an "act of racism," chastising them for letting politics get in way of confronting "a sickness that is crippling our nation."

Carson, a retired neurosurgeon and so far the only African American of either party running for president, was blunt in an op-ed published Monday in USA Today:

Not everything is about race in this country. But when it is about race, then it just is. So when a guy who has been depicted wearing a jacket featuring an apartheid-era Rhodesian flag walks into a historic black church and guns down nine African-American worshipers at a Bible study meeting, common sense leads one to believe his motivations are based in racism. When the sole adult survivor of the ordeal reports that the killer shouted before opening fire, "You rape our women and you're taking over our country. And you have to go" — well, that sounds to me a lot like racial hatred.

The comments were a bold departure for Carson, who gained celebrity status within the African American community for his story of rising from poverty to become one of the most celebrated doctors in the world -- but has since become known for embracing a hard-right brand of conservative politics.

A recent Washington Post analysis of polling by the Pew Research Center showed that half of white people — and 6 in 10 white Republicans, who Carson needs to win over during the presidential primary season — see no racial discrimination around them. By contrast, only 13 percent of African Americans don't see racism.

In the wake of the shootings, some Republican candidates have struggled with whether and when to label the attacks racist, instead suggesting that the shooter might have been motivated by religious intolerance, or was simply mentally disturbed.

[Can diverse faces in GOP sway minority voters?]

The candidates have also found themselves pressed to respond to a growing chorus of activists and politicians critical of the decision not to lower the Confederate flag, which flies on the grounds of the South Carolina state capital. After former GOP presidential candidate Mitt Romney tweeted over the weekend that the flag should come down because many saw it as "a symbol of racial hatred," several candidates weighed in to say they personally agreed with Romney, but that the decision should be left up to South Carolina.

Carson did not address the flag in his op-ed, but he did knock "people who are claiming that they can lead this country who dare not call this tragedy an act of racism, a hate crime, for fear of offending a particular segment of the electorate."

Chris Christie's PAC, Leadership Matters for America, called our attention to a video of remarks he made Sunday at St. Mathew AME Church in Orange, N.J.

"This hate didn't come from nowhere. This hate didn't just appear out of the sky," he said from the pulpit during a prayer service for the victims of the shooting at Emanuel AME Church in Charleston. "This hate comes from an awful place; this hate is born of racism and we must say that out loud."