The epoch of imperialism cannot permit the existence, in a single party, of the revolutionary proletariat’s vanguard and the semi-petty-bourgeois aristocracy of the working class, who enjoy morsels of the privileges of their “own” nation’s “Great-Power” status. The old theory that opportunism is a “legitimate shade” in a single party that knows no “extremes” has now turned into a tremendous deception of the workers and a tremendous hindrance to the working-class movement.

— The Collapse of the Second International by Vladimir Ilich Lenin