On the morning of March 14, 2016, in a tiny office in Rio de Janeiro, a libertarian businessman named Winston Ling met with Jair Bolsonaro, a right-wing congressman running a longshot campaign to be president of Brazil. Some of Ling's closest associates had pleaded with him not to sit down with Bolsonaro, who was infamous for public comments praising torture and dictatorship and denigrating women and minorities. Just associating with him, they feared, would tarnish Brazil's libertarian movement, which was drawing new followers at an astounding pace and winning mainstream recognition. Three...