> It depends on your definition of racism, and most scholarly definitions are "power and prejudice." In other words, a white person who is in the majority has more power than a black person (think Silicon Valley[1]), so the actual impact of the prejudice has a greater magnitude that turns it into "racism."

I don't know what scholarly sources you've seen that use that definition, but most scholarly sources I've seen define don't factor power into the definition of racism, but do certainly acknowledge that power dynamics have a pretty big impact on the effects of racism.

OTOH, the "only people in positions of power can be racists" thing is something I've seen pretty much exclusively in non-scholarly sources.