Cavani and the incident in question are not really the point. The point is all the hemming and hawing that goes with it, especially when people start making justifications that suggest other cultures are allowed to be racist.
South America is a deeply racist place, just because people of color may seem to go along with it doesn't mean anything, and whether or not people are friends is entirely beside the point. It's not simply a question of language, either. It's a symptom of deeply entrenched racist cultural norms and systemic oppression that mutually reinforce each other. When you isolate one from the other, you get these kinds of arguments found in this thread. When you make it specific to an interaction between a few people, it becomes anecdotal. The reality is that all these are connected in a clearly traceable history of racism that nobody is exempt from, and certainly not South American ffs.