(Fascinating trivia: California allowed open carry until the Mulford Act in 1967 restricted it -- directly in response to the Black Panthers practicing it. The Act was signed into law by Ronald Reagan, with the explicit support of the National Rifle Association.)
Edit: I mean, come on: https://www.youtube.com/watch?v=1eVPKpBKGCE
People have done tests with white people and black people open carrying in exactly the same way. Black open carriers got a very different police response.