This forum is about wrong numbers in science, politics and the media. It respects good science and good English.
Not all that long time ago, if a person found him or herself among others who did not look the same, odds were very bad for that person to continue to live all that much longer. Simple as that.
It was survival of the individual person that caused racism, and if one looks around as of now, nothing has really changed.
Racism is all about survival, even to this very day.