... sure ... but you don't prepare a kid for racism with a sheltered upbringing in a pretend world where discrimination doesn't exist. You point out bad behaviour and tell them why it's not OK.
My son is three years old, he has two close friends - one is an ethnic minority (you could live an entire year in my city without even walking past a single person of their ethnic background on the street). His other close friend is a girl. My kid is already witnessing (but not understanding) discrimination against both of his two closest friends in the playground and we're doing what we can to help him navigate that. Things like "I don't like him he looks funny" and "she's a girl, she can't ride a bicycle".
Large Language Model training is exactly the same - you need to include discrimination in your training set. That's a necessary step to train a model that doesn't discriminate. Reddit has worse discrimination than some other place and that's a good thing.
The worst behaviour is easier to recognise and can help you learn to recognise more subtle discrimination such as "I don't want to play with that kid" which is not an obviously discriminatory statement, but definitely could be discrimination (and you should probably investigate before agreeing with the person).