Harris, Twain and Foster were called racists because of the slave vernacular. Harris didn't even write the Uncle Remus stories, they were told to him by an old slave when he was a boy and he simply wanted to preserve them. He was embarrassed when people praised his Remus works because he merely took dictation.

If Huck Finn is a racist work, you got me hanging. The part where Huck plays a mean trick on Jim and Jim tells him about the time he slapped a little slave girl for not doing what he told her only to discover later that she was deaf and he walks away leaving Huck standing there realizing he owed Jim an apology and says, "It was fifteen minutes before I could humble myself before a nigger." I thought it was one of the most touching passages in all of Western literature. Instead of portraying Jim as a happy-go-lucky shuffling darkey, Twain portrayed him as a man that even though he was a slave, he too was haunted by guilty memories. You saw past the old slave vernacular to the man himself. That he was just like you and me.

And Foster was antislavery. His use of the slave vernacular and words like "darkey" were simply common in his day. When you look past the un-PC language to the intent behind the words, there's nothing racist to see.