I just got thinking about this and really cannot think of a possible answer to it. In old literature, for example, the works of Shakespeare (which I know were plays but this question may still apply to it), from before there was any sort of aversion to racism, and in some cases, an encouragement to discriminate against anyone of a non-white ethnicity, are there any prominent examples of racism, which no-one would have really noticed as it was the norm, but which would get a writer today jailed, or even any underlying tones of racism?
As I already wrote on another occasion, How did people categorize each other in the middle ages, how did racism work? racism seems to be a relatively modern invention. In the works of historians of ancient Greece and Rome I could not find ANY trace of it. To the extent that we do not know from the work of these historians what was the race or skin color of the main personages. (What was the race of Hannibal? What were the races of African kings who waged the wars with the Romans?) It seems that this situation prevailed until the Enlightenment age, or perhaps even later.
It seems that the very word "race" did not appear in European languages before 17 s century. I challenge anyone who voted this answer down to give a reference for the use of the word "race" before 1600.
EDIT. Of course all kinds of discrimination by religion, language, noble or not noble origin and even a place of birth were very common. But "race" was not. The notion of race is of modern origin. Race is a "biological" notion, or more precisely pseudobiological, based on skin color, form of eyes, nose, hair etc.