The gent in St. Louis is a well-to-do lawyer, and if he's smart he'll use this as a step stone case for the Supreme Court to settle these type of cases once and for all.
As for the question whether CHL insurance would have helped him -- I don't know for sure. He was on his property, open carried his rifle, and did point it at a potentially threatening crowd. I don't know whether such actions are covered under CC insurance. I personally don't have insurance and never really considered it.