It was a mural if it were sanctioned by the community; either painted after civic permission of some kind were granted, or on private property with permission. Anything else is graffiti and is a crime. You cannot “deface” graffiti, you can only add to it, or clean it up.
“a city-approved Black Lives Matter mural in Martinez, California,”
So see the city approved this but I wonder if they asked all citizens of all colors how they felt before they spent their tax money on it.