There's environmentalism and anti-immigrant sentiment in the online writings of the now-deceased Discovery Channel hostage-taker, James Lee -- more of the former than of the latter. I'd say he was somewhat more left than right.
But nobody -- right, center, or certainly left -- ever followed where he led; back in 2008, it appears that he literally paid homeless people to protest the Discovery Channel with him.
Maybe that's because his ideology was less leftist or rightist than anti-Discovery Channel-ist. It's also because elimination of the human population, one of the key elements of his manifesto, isn't exactly a cause on either political side. (Sorry, pathetic right-wing "think"-piece authors, I'm dismissing in advance the attempts I'm sure you'll make to argue that a belief in population elimination is left-wing because we support reproductive choice, or because we, at least in your fevered brains, hate Sarah Palin for not aborting Trig.)
Want a sad experience? Go read the message board Lee (aka "misterfifteen") set up for his 2008 Discovery Channel protest. He receives sincere but thorough criticism from a poster named wildforwildlife; after that, he's mocked mercilessly by everyone who drops by. His most persistent mocker drives a Prius and recommends the movie Koyannisqatsi -- I don't think this person is a Limbaugh fan. Other posters express environments bona fides -- but think Lee is delusional, especially when his protest seems to consist of nothing but himself and some rent-a-protestors. Lee may have gotten a fair number of his ideas from the left, but no one on the left -- literally no one -- went where he tried to lead them.
(Links via Rumproast.)