There's a lot more to it than initially meets the eye. No one is suddenly offended by the confederate flag, any more than they were suddenly offended by the other 4500 'politically correct' cultural communism things that suddenly became highly offensive.
There are also attacks on the UNION flag as well, which should tell you something. UC Irvine student union took it down because they felt it was unwelcoming to students. The very idea of nations and borders is under heavy attack by globalists and the leftist thugs they fund to push out their twisted messages. If you want to keep your country from being flooded by 6 billion refugees from the overcrowded parts of the world you are a racist.
As for it being about slavery, the flag definitely is nothing to do with it. How much that was responsible for the war is unclear but there's a lot of facts most people are ignorant of (especially if they come from other countries). For one, the north offered a guarantee to NEVER end slavery if the south would not secede. The north also had several slave states fighting on its side. Lincoln also strongly advocated returning all blacks to africa.
I think it worked out fine to have a black minority in America and the world did not end. I don't approve of what this is about, though, which is suicide for the natives to embrace. That's demolishing all national identity completely, disarming population and flooding it with ever increasing numbers of immigrants. Obviously that is not something sustainable in the long run. Countries that overbreed need to stop breeding so much. While western countries need to close their borders and improve their economies again so that the natives can raise children in the lifestyle they had as kids, which is completely impossible today for 99% of the population.
If you disagree though you are 'racist'. You were 'racist' for opposing NAFTA for God's sake. No offense to mexicans or chinese or indians they are fine people. But they could (and largely already have) completely flood the country and drive the quality of life here into the toilet by lowering wages and driving up prices.