I left the insurance industry about 13 years ago. That was actually a happy day in my life. Did things change that much? In my day we covered on an "All Risk" policy such things as riot and civil commotion.
On the other hand, if I owned a business in Ferguson I would negotiate with my insurer to let me rebuild somewhere such that local denizens don't try to ruin me because of an event like this.
I don't know what happened there. I doubt Wilson was looking for guys to gun down. I doubt he was hunting for the most dangerous game.
I do know there must be somewhere to build a business where the locals don't blame me for something I can't control. I would ask my insurer to assist with that, maybe for a discounted payoff.
It started after the 1992 LA Riots; yes, the industry did change. Now your basic commercial policy specifically excludes civil unrest, riots, looting, etc., etc. This became de rigeur (at least for the clients I provide with IT services) about a decade ago. If one wished to have those covered, you had to pay more.
In the event they *were* actually covered, the insurance companies will actually work with their clients to help them rebuild elsewhere, as a general rule. The alternative for a business that chooses to rebuild in the original location is an enormous raise in premiums.