The anarchists and communists of a century ago were highly assimilated. Old-fashioned Orthodox Jews of the shtetl were not anarchists and communists.
Of course they were (assimilated.) We're talking of perceptions at the time (right or wrong) of the source of the problem.
Fukuyama argued, quite persuasively, I might say, that these Islamist radicals are actually produced in the West! Ouch!