Actually, they never went away. Patrick Moore, cofounder of Greenpeace, left Greenpeace when it became to radical for him! After the fall of the Soviet Union all the west's leftists needed somewhere to go, and they picked up on the environmental movement. It didn't matter that capitalist countries have better environmental records than communist countries--because they don't really care about environmentalism. They care about ending capitalism.
You don't believe me? Perhaps you'll believe your not-so-lying eyes. It's been awhile since I've linked to Zombie's work, but he's still the preeminent photojournalist of our age. And yes, these communists are here in the People's Republik of Kalifornia, in lovely downtown Oakland.
If I wanted to get rid of them for good I'd just tell Raiders fans that those commies are Denver fans. That would take care of the situation pronto.