Full article: https://psmag.com/social-justice/an-end-to-horseshoe-theory
Philosopher Jean-Pierre Faye looked at the Molotov-Ribbentrop Pact and other instances of right/left coordination, and decided that they were no coincidence. Instead, he believed the confluence could be explained by what he called Horseshoe Theory. Horseshoe Theory says that the right and left are not on opposite ends of a linear political continuum. Instead, the political spectrum is bent, like a horseshoe, with the far right and far left at the ends bending around so they almost touch each other.
For centrists, and for right-wingers, Horseshoe Theory is a convenient chunk of heavy iron to toss in the faces of left-wing opponents. But its very convenience should be treated with suspicion. Everyone loves to hate the left. But hating the left isn't a good way to fight right-wing extremism. On the contrary, the conflation of alt-right Nazis with a supposed "alt-left" gives people like President Donald Trump and former Breitbart Chairman Steve Bannon rhetorical cover to slime their critics as the "real fascists." Perhaps even worse, claiming that the left is especially prone to fascist tendencies allows folks on other parts of the political spectrum to ignore their own complicity when actual fascism crawls out of the mud.