I honestly thing Dan could have said it diffrently to get his point across. He left gimself open for misinterpretation there.
But that still doesn’t make him racist. Or the other dude(s) correct.
With millions of people living in europe at the time, is it possible there were a very few black people in central europe at the time through wildly unusual circumstances? maybe.
But were they normal? Nope.
One of the things making KC:D great, is that it is dedicated to staying true to historical reality and depicting things within the bounds of “normality”, not freak singular occurances, especially with the character(s).
So even if one could prove or assume the existence of some POC in bohemia in 1403, they would be so freakishly rare, that including them in this game would be going against the historical plausibility aimed for.