I disagree with one detail: once a child is old enough to know that racism is wrong, they should be exposed to books like the one Valenti mentions. Learning this stuff, just like learning about WW2, is important to teach children about the mistakes (and evils) humanity has committed.Of course, when a child is too young to understand, and easily impressionable, you don't want to expose them to any shit like this.For example, Nazi propaganda is displayed in the Holocaust museum, and as a middle schooler, I found it unbelievably illuminating. There's a time and a place for everything.Maybe don't ban it, but definitely age-restrict it.
If you don't make the cartoons disturbing, you can already explain to kids how some bad people existed in history, and why they were bad, etc.....
These types of issues are insanely frustrating, because there's a need to balance a desire to raise open-minded, educated children, with a need to uphold the principles of American law. That being said, and although it pains me to do so, I would have to disagree with banning racist or otherwise inaccurate children's books from libraries. In history, banning books has always been a sign of an increasingly autocratic society, and a government should never have a right to limit creative expression, no matter what it expresses. Keep in mind, The Catcher in the Rye and Huckleberry Finn were both widely banned across the US for decades, because society at the time believed it taught kids about homosexual behaviors and held anti-religious sentiments, which were considered wrong. Its too easy for a society to decide against a certain idea or concept and condemn it, and then have the ramifications of that come back to bite them years later, because they've set a precedent of censorship. A better solution would be to keep those books, but have a mandatory class in schools about the history of prejudice in our society, and how we've overcome/ are working to overcome it.
Given the prevalence of these things in society, (via literature, movies, tv, etc etc), I don't think the question is whether or not kids will see these things, but rather the context in which they first see them. From this perspective, I'd personally prefer if they were introduced to this in a more or less controlled environment (school libraries), where they can be given context, explanations, or warnings about what they're seeing, as opposed to out in the wild where none of that might be possible. After seeing these things in schools, kids would also be better prepared when, inevitably, they come across these sorts of things later in other parts of their lives.