Those trying to understand the ease with which Marxists can turn themselves into fascists – a process of seeming polar reversal exhibited by so many neocons – might consider the insight provided by one of 20th century America’s greatest minds, Eric Hoffer. Addressing “the interchangeability of mass movements,” Hoffer observed:

“When people are ripe for a mass movement, they are usually ripe
for any effective movement, and not solely for one with a
particular doctrine or program. In pre-Hitlerian Germany it
was often a tossup whether a restless youth would join the
Communists or the Nazis. . . . Where mass movements are in
violent competition with each other, there are not infrequent
instances of converts – even the most zealous – shifting their
allegiance from one to the other. . . . One mass movement readily
transforms itself into another.”

Eric Hoffer, THE TRUE BELIEVER (1951).