Sure, you can and should if you're aware of the challenge and care enough to combat those biases. It might feel like second nature for some, but it can also be like a muscle that needs to be exercised for others. It sounds like they're trying to do so now, and that kind of growth should be encouraged imo.

Considering how many people will either assume they're open minded enough already without really reflecting on if there's room for improvement or actively go out of their way to treat others like they're inferior, I don't see the value in dragging other folks down for attempting to be more conscientious towards others. Who knows - maybe another future former racist will read their comment and come to the same realization.