Fox News host Tucker Carlson, whose race-baiting screeds have the approval of chairman Lachlan Murdoch, stepped up his attacks on frequent target Don Lemon on Thursday night, labeling the Black CNN anchor the “slowest person ever to appear on cable news.”

After President Donald Trump repeatedly boasted that he could recall five words during a cognitive test, CNN anchor Chris Cuomo teased Lemon for misidentifying a picture on the acuity exam during their Wednesday night handoff. Carlson, meanwhile, used that moment to question Lemon’s intelligence.

“What does it mean if you don’t know a rhino from an elephant? Well, you may not be a physician but I think you know what it means. It means a low acuity and that’s not a surprise in the case of Don Lemon,” Carlson declared, purposely mispronouncing the CNN anchor’s name. “A perfectly cheerful person but he may be the slowest person ever to appear on cable news.”

Carlson, currently under fire within his own network over his show’s racist content, went on to say that the primetime rival “combines supernatural slowness with remarkable self-confidence.”