Because bigotry comes only from one side, the KKK, NAZIs, and white nationalists. The other side is opposed to bigotry, that's why they marched in opposition. There isn't bigotry on all sides, just the one side, the Ku Klux Klan, the white NAZIs, and the white nationalists. The other side was fighting against bigotry. It's totally simple. If you march against black people, you are a bigot. If you march against bigots, you are not a bigot.