More on the difference between racial discrimination & racism, in Robin DiAngelo's White Fragility. On p. 22 of my copy:
Racism is deeply embedded in the fabric of our society. It is not limited to a single act or person. Nor does it move back and forth, one day benefiting whites and another day (or even era) benefiting people of color. The direction of power between white people and people of color is historic, traditional, and normalized in ideology. Racism differs from individual racial prejudice and racial discrimination in the historical accumulation and ongoing use of institutional power and authority to support the prejudice and to systematically enforce discriminatory behaviors with far-reaching effects.
People of color may also hold prejudices and discriminate against white people, but they lack the social and institutional power that transforms their prejudice and discrimination into racism; the impact of their prejudice on whites is temporary and contextual. Whites hold the social and institutional positions in society to infuse their racial prejudice into the laws, policies, practices, and norms of society in a way that people of color do not. A person of color may refuse to wait on me if I enter a shop, but people of color cannot pass legislation that prohibits me and everyone like me from buying a home in a certain neighborhood.
People of color may also hold prejudices and discriminate against their own and other groups of color, but this bias ultimately holds them down and, in this way, reinforces the system of racism that still benefits whites. Racism is a society-wide dynamic that occurs at the group level.
When I say that only whites can be racist, I mean that in the United States, only whites have the collective social and institutional power and privilege over people of color. People of color do not have this power and privilege over white people.