You have to understand the basic way of thinking involved. To these slavery and Jim Crow nostalgics, it’s a matter of power, and only one race can be in power. The monument to the “battle” in front of the old Customs House put the matter explicitly in the inscription that was altered back in the 70s. It said that the white heroes had died trying to restore White Supremacy to Louisiana. To this way of thinking, we either have White Power in charge, or we have Black Power on top, and they just can’t imagine any middle way, any actual democratic rule in which no ethnic group has the power to lord it over the other.
What they would say to your argument would be that one group or the other, blacks or whites, has to be silent and subservient, and it’s not going to be the white people. Free speech can only be free speech for white people, and white people simply have to oppress blacks, now, in the past, and forever.