As arrests during a two week long civil action against the Keystone Pipeline XL in Washington DC rose to nearly 600 people, Bill McKibben, head of 350.org, and Robert Bryce, Manhattan Institute for Policy Research, debated the issue on PBS.
While activists oppose the massive pipeline (from Canada to Texas) for a variety of reasons, including potential oil spills, the major issue at stake is climate change. Oil from tar sands carried a significantly heavier carbon burden than other oil sources. Many activists have come to view the Keystone Pipeline XL as a litmus test of sorts for the Obama Administration, which has largely disappointed them on environmental and climate issues.
To read more about the protests: Over 100 protestors arrested as civil action begins against tar sands pipeline to US