WASHINGTON — Matt Schlapp, the pro-Trump chairman of the American Conservative Union, had a remarkable on-air clash not long ago with his old friend Michael Steele, an anti-Trump former chairman of the Republican National Committee.

At issue was Mr. Schlapp’s defense of Ian Walters, the conservative union’s communications director, who told an audience: “We elected Mike Steele to be the R.N.C. chair because he’s a black guy. That was the wrong thing to do.”

Mr. Steele invited Mr. Schlapp on his radio show the next day and berated him: “Do you know how that sounds to Americans? And do you know how they then equate that level of stupidity to conservatism?” Mr. Schlapp apologized, and pointed out that Mr. Walters had, too. But he chastised Mr. Steele for being “critical of some of the more conservative aspects of the Trump phenomenon,” adding, “You need to have some grace.”

Mr. Steele blew up: “I’ve spent 41 years in this party, 41. I’ve taken crap you have no idea about.” And finally: “There’s only one word I can say and I can’t say it on this air.” The two men haven’t spoken since.