Why did people after world war ii believe that conservatism was "a relic of a discredited past"?

People believed that conservatism was "a relic of a discredited past" as it supported anti-Semitism, had a preference for a social hierarchy as well as a proclivity for conspiracy theories which were now deemed a thing of the past. Conservative parties across central and eastern Europe were destroyed or co-opted by the totalitarian regime of Nazi Germany in the period  leading to World War II

i think they came to washington to protest