I agree with Corey Robin on this:
During the Vietnam era, liberals and leftists believed not only in social justice but also in mass protest. Whether the cause was democracy at home or liberation abroad, men and women afflicted by oppression had to organize themselves for freedom. Yes, some of yesterday’s activists were blind to coercion within these movements, and others joined elite cadres bombing their way to liberation. Still, the animating faith of the 1960s was in the democratic capacities of ordinary men and women, making it difficult for liberals and leftists to believe in conquering armies from abroad or shock troops from on high.
Many liberals, and some leftists, no longer hold these views. Their faith is guided not by the light of justice but by the darkness of evil: by the tyranny of dictators, the genocide of ethnic cleansers and the terrorism of Islamist radicals. Despite their differences—some of these liberals and leftists support the war in Iraq, others do not; some are partial to popular movements, particularly those opposing anti-American governments, while others favor constitutional regimes, particularly those supporting the United States—theirs is a liberalism, as the late Harvard scholar Judith Shklar put it in a pioneering essay in 1989, that seeks to ward off the “summum malum” (worst evil) rather than to install a “summum bonum” (highest good). Reversing Augustine’s dictum that there is no such thing as evil—evil being only the absence of good—today’s liberal believes there is only evil and progress is measured by the distance we put between ourselves and that evil.
Ah good intentions and the obsession with evil...