LOL, I had the same initial reaction. Apparently Norse monitors global cyber attacks[1]. So the real question is not why they hate St. Louis but why does China hate St. Louis?
I found the link while reading conspiracy theories about the NYSE shut down this morning[2]. I have no idea about the quality of the data. I just thought the visualization was cool.
Norse Corp. is a threat intelligence company. I believe one of their HQ is located in St. Louis and is where they currently host many of their honeypots. That is why you see St. Louis being attacked a lot.
That's because of all the defense / Intel work in St. Louis (Scott afb etc). And to the other commenter talking about Kirksville, that's where the JSS is.