Without spending much time on it, it's clear that several things stated about the map are not true. e.g. the data are not
aggregated by county (not too many spherical counties around.) And whatever "normalized for the number of tweets" means.
It's not clear that valid methodology was used at all.
For what it's worth, if you zoom all the way in, the red blob of hate in the northwest isn't over any town. It becomes a dot centered directly over my property, in fact.
(I do not now and have never tweeted. Maybe the dog?) That big angry blob that looks as if it covers millions of people at the national map scale looks like it's just one solitary kook at the zoomed-in scale. (And apparently it's only associated with use of the word "dyke" and nothing else.)
I wouldn't waste too much time interpreting this mess.