I don't think they're smearing. There is a cluster of white nationalist groups in southern Indiana but I don't think that means people are generally more racist there than say, Ohio.

The two things I take away from looking at the map are 1) it's not just a southern thing (which I think is a misconception they're explicitly trying to correct) and 2) the hate group density correlates with population centers pretty well (which is often the case for maps of people).