It's been my experience that for every 1 genuine mistake there's like 20 people who just don't do it around you. I take a noninterventionist and moral neutrality stance when interfacing with people, and you wouldn't believe how many people think that means they have carte blanche to drop all kinds of slurs around me in private when they think nobody else is listening because they think my lack of pushback is because I agree with what they're saying, not that I vehemently disagree but would rather they be open about their vile views than just mask them up.

Listening then pointing out contradictions in their reasoning goes a lot more to actually tackle the racism than telling them to shut up does.