You can define racism as prejudice plus power, and lot of people seem to want to do that. This definition has a lot of the problems you point out here. I'd don't like the idea of redefining common words so you can show that you are smarter than other people. (See "Abolish police" supposedly meaning "get them to do something else".) However, If you want to talk to these people about racism as it exists amongst marginalized people, just call it prejudice, and move the discussion on from there. Everybody still agrees that prejudice is bad, and that racism is worse. If you don't talk to people with the meanings they have chosen you end up talking past each other.