I've experienced this in various forms with both my white and black kids. I just misdirected the kids thinking they're too young to be burdened with those concepts. I don't think there'd be anything wrong in confronting the other parent....just not my style. I would LOVE to see them be confronted by somebody else though....perhaps not in front of the kids. I don't know. It's not hard to difficult to misdirect the kids so that the issue doesn't become explicit to them. Not sure if that's the right thing in every circumstance. I just don't think there's much pragmatic function or value in trying to explain racism to a kid under the age of around 8 or 9. (also depends on the particular kid's intellectual development level)