radicalism has definitions from the field of politics
[ noun ] (politics) the political orientation of those who favor revolutionary change in government and society

Used in print

(John Michael Ray, "Rhode Island's Reactions...)

The Warren_Telegraph stated that many of Rev._Trafton 's remarks were inappropriate and savored strongly of radicalism and fanaticism .

(John Dos Passos, Midcentury....)

For once radicalism was a recommendation .