it might be beneficial to do some further reading in advance to learn about favela history and culture. this can prevent accidentally inappropriate remarks and awkward situations.

however, no matter how educated or conscientious one may feel or try to be  about favela history and culture, a visitor should always defer to the knowledge and views of a carioca, who by definition has a much deeper and broader understanding.

external opinions about favelas are likely to cause offence, or at least discomfort, even when a carioca does not openly say so.