Thanks. A lost fact of history is that the ACLU was almost legally outlawed as a Communist front just before World War II, but Morris Ernst cut a deal with the FBI to purge the ACLU of known CP members and inform the government on left-wing activity in the legal community. At some point it's clear the ACLU reneged on this deal and the Communists were able to reassert their original influence in the organization--I would guess this probably happened with the rise of the Vietnam antiwar movement and the disintegration of the Cold War consensus. Today, I think you could make a good case that in the context of the War on Terror, the government should again review the ACLU's legal status. Likewise the National Lawyers Guild.
They can't recruit the necessary cannon fodder here, and they're finding it impossible to penetrate the multi-layered defenses of our homeland security, so they use Marxist fifth columnists as the tip of their spear.
David Horowitz was prescient when he warned of a Red-Green alliance.