Im not white, but I grew up in the US and know that racism, racist thoughts, and activity is deeply insidious. You have to dig deep, examine all your actions and thinking and the winnowing out of bigotry (of any kind) can be exhausting as it is a rigorous activity and you are never ever sire you got all of it. It’s like a kind of oil poured on one’s life. It seeps into any undefended nooks and crannies, and is often perpetrated out of sheer ignorance.