A quiet, but effective undercover agent should be able to take out this nutjob and all around him - we just need the right opportunity.
Everybody called Winston Churchill a nut job when he advocated assassinating Hitler in 1936. How many million lives might have been saved by one bullet?
By the same token, Herr Hitler was possibly the most incompetent military leader in history, and crazy to boot.
If one of his smarter, saner, but equally evil political rivals had taken his place. . .