How, exactly, is the theory of evolution "racist"?

It isn't in any stretch of the imagination. If anything the diversity of human physical characteristics shows that no one race is superior to another. There was (and in some cases still is *cough conservative Americans cough*) in cultural evolutionism, generally the belief that all societies would one day become like Western society (as the pinicale of civilisation *rolls eyes*), they were just behind on the evolutionary scale. Any decent anthropoligist will tell you this is manifestly untrue too.