White Southerner here. Southern culture is NOT all white, and most of us are actually aware of that.
When I think of southern culture I think of southern hospitality and sweet tea, neither of which are limited by race.
I’ve lived on 3 continents and every culture has individuals that are racist. By far the worst was when I lived in a homogeneous Asian country - people felt the constant need to stare and comment (and because I’m white they were trying to say NICE stuff) and it made me so uncomfortable. I have no idea what it’s like to be black, but I got a glimpse of how people will made dumb assumptions about you based on your skin.
The biggest key to defeating racism is melting the pot further - which the South is doing. Yes, there are plenty of racists here, and plenty of racists communities, but I can guarantee you they exist elsewhere too. Fighting it only happens when we confront it.
John Oliver did a great bit on school segregation that goes into how racism isn’t a Southern issue.