A previous post on racism is here.
This is a big picture, philosophical look at racism or racisms (as in Francisco Bethencourt’s Racisms: From the Crusades to the Twentieth Century, Princeton University Press, 2014). It is also historical, although that is incidental to the philosophical progression.
Racism means treating people differently (e.g., negatively) depending on their race. Here races are understood as varieties of the human species (or kind), which are often associated with ethnic and cultural characteristics. Racism is wrong in an ethical sense. However, taking ethnic and cultural characteristics into account is acceptable as a social grace or for effective communication.
Realist racism is based on the doctrine that different races are different in kind, not merely in degree. So the various associations with race are considered as characteristic of the natural or created kinds. That implies there is nothing one can do to change these characteristics. If a race is considered slaves by nature (barbarians to the ancient Greeks), then that is what they always were and always will be. From this position an equality of races makes no more sense that an equality of apples and oranges.
Eugenic racism is the doctrine based on evolutionary biology in which races are different population groups, which could interbreed to form new races or be kept separate and maintain divergent traits. In evolutionary biology a single-race population might even become a new species. Because of the evolutionary descent from primitive organisms, it is possible that different races might be earlier or later in the evolutionary tree. This is taken as a justification by eugenic racists that breeding practices applied to animals should be applied to humans as well, in order to purify or perfect a racial group.
Identity racism is based on the doctrine that different racial identities (including related ethnicities and cultures) should be allowed to flourish on their own to ensure their development without interference. Identity racism supports race consciousness and race politics. The relation between races may be viewed as egalitarian or not. What matters is that independent racial development must be maintained for the sake of civil rights and social justice. Today non-egalitarian identity racism is widely condemned, but egalitarian identity racism is not widely recognized for its own racism.
The Western ideal has been individual development, apart from race. An ideal of collective development might also be different from race. In any case, we should focus beyond race to the development of our individuality and common humanity.