Who did blackface hurt or harm? How do we know?

they harm the black people. Because they was stereotyping black people

Answer: The Black community.

Explanation:

Blackface is when a person of a lighter skin tone puts on black or brown paint on their face in order to make fun of a person of color. It began after the civil war, primarily used in plays by Caucasian actors playing black roles in an attempt to mock them.