I don't think there is a real magical distinction between "white" and "black" magic. That was a social distinction that arose due to race relations in medieval Europe.
Normally my lectures are longer than this one and I always talk about the motivations behind the magic which have often been characterised as 'white' or 'black' but which in modern parlance might be described as help or harm. Most of the practitioners which we know a lot about from the past fell somewhere in between the two. I don't think race was ever a part of that.
