The topic for this thread is misleading. The linked article is about a different topic, and its author is already outside the Democratic Party. The article is about tar sands and the Keystone XL pipeline. The author of the article is the media co-ordinator for the Green Party. He's making a sales pitch for his party. Fracturing the Democrats is incidental to his goal. Oh, and I liked what ecib said.
I don't consider the title to be misleading. The article does speak at length about the Tarsands and Keystone XL, but it's only used as a wedge issue to deface the Democrats. Other issues are discussed as well. Obviously any article answering the question "Should progressives ditch the Democrats?" is going to discuss fracturing the Democrat party. I considered the Green party affiliation of the author when I added the #greenparty tag.