If you expect some kind of people to be in charge rather than others, it is a symptom of widespread racism/sexism in your environment. You doing the "mistake" does not mean you necessarily, actively, try to cause harm. But you still do, and this wouldn't happen if not for racism.
> Why would the person on the victim end of this feel humiliated?
For the person doing the mistake, it was one particular case of embarassment, for the victim it was Tuesday. The constant rate of mistakes make it humiliating.