Wingnuts have been around since at least the 19th century. Teddy Roosevelt coined the term “lunatic fringe” to describe them. In the 1950’s there was McCarthyism and the John Birch Society prompting the “red scare” where so-called communist sympathizers were ostracized. On the left there were radicals like the Black Panthers. Fringers often compare politicians in power to tyrants like Hitler or Stalin.
Excommunications and defections were on the rise. Defectors included Chris Buckley (son of William F. Buckley), David Frum, David Brooks, Peggy Noonan, and Andrew Sullivan, each declaring in some way as Independents. Criticizing the extremists raised the ire of their followers and those that did got the heretic branding, as those on the right who criticize Trump do today.