I have never heard anyone make the argument that racism is prejudice and [with] power. Do you have a personal or media example of it?
I have always understood that a racist is person whose behavior reflects racism - acting against others due to their race, regardless of whether the racist had any power by which to enforce their racist intent.
Is the KKK no longer racist and no longer practicing racism because they have no power? No. Power may make racist intentions more powerful, but the racism is there even when there is no power.
But I digress. I really never heard a Liberal make the argument you suggest we might have heard from a Liberal.
https://www.bbc.com/news/world-us-canada-52993306
Which started in the 1970’s
https://medium.com/handwaving-freakoutery/the-two-confusing-definitions-of-racism-2d685d3af845