"Racism is power +prejudice" No that is the way some people use the word. But that isn't the only use of the word. generally the word is used to mean any sort of racial prejudice. Words have multiple definitions and meanings depending on their various uses. And really it's only a small amount of people (SJWs and people in sociology departments) that use the power+prejudice definition. All prejudice based on race or ethnicity is racism.
You just admitted that people who study sociology define racism as prejudice plus power. They do. And I would be more inclined to believe them then someone telling me that being mean to one’s oppressor is racism. In your definitions, racism and prejudice are the same thing, but they aren’t. Anyone can dislike a group of people for whatever reason but if they have the power to hurt said group that is when it becomes racism. Your definition potentially victimizes the oppressors, whereas sociologists’ definitions names an oppressor and the oppressed. Is your version better?