Before the “black helicopters” of the 1990s, there were right-wingers claiming access to secret documents from the 1920s proving that the entire concept of a “civil rights movement” had been hatched in the Soviet Union; when the landmark 1964 Civil Rights Act was introduced, one frequently read in the South that it would “enslave” whites. And back before there were Bolsheviks to blame, paranoids didn’t lack for subversives — anti-Catholic conspiracy theorists even had their own powerful political party in the 1840s and ’50s.