I’d say it’s less that they are an idiot and more that they don’t understand there is systemic racism and interpersonal racism (there is probably a more official term here but interpersonal covers it well enough for a Lemmy comment).

Systemic racism can only be done by the majority group with the power in a given system (usually government but it could be perpetrated in a religion, an institution, club, etc.). Red lining is a great example of that. Segregation as well. Things done by the group in power to the ones not in power of the given system. Throughout the history of the USA, this means white people oppressing other ethnicities but especially black people.

Interpersonally, anyone can be racist. They can hold racist views and hate others without knowing them beyond their appearance.

Edit: strike through on majority. While most commonly it is a majority group in power, it doesn’t have to be a majority group, just the group in power.