Never mind that Craig Cobb is stupid. Is he also blind? There is no suggestion that he is, so of course he knew that he was part-black.
No wonder that he has a beard, but it achieves his end in wearing it about as well as Marvin Gaye's would have done if it had had the same purpose.
14 per cent Sub-Saharan African ancestry suggests, either that Brother Cobb has several quite distant black ancestors perched on different branches of his lineage, which admittedly would be amusing, or, far more probably, that his one black ancestor is none too distant.
Possibly close enough to have been known personally to him. Certainly close enough for him to have grown up aware of the situation. Even before he had looked in a mirror.
Raising all sorts of questions about what drives him. Above all, about what drove him to submit to that televised test. Knowing full well what the result was going to be.