This is not about racism or discrimination.

It is about having a degree of sensitivity, or at least a degree of social awareness, that if you put on blackface and dance in a major city where there is a significant population of non-white British (but as British as anyone else) then you might expect to called out about it.

If you live in some RoI backwater, or yokel Lincolnshire, or Shitkickshire, then you really have no idea or more likely don't care