Yes, the extraction process is dirty. But the real risk lies in the carbon emissions from the extraction process and eventual use of the extracted oil as fuel.
The truth is that the tar sands gook contains more than twice the carbon from all the oil burned in human history. If infrastructure, such as the Keystone XL pipeline, is built to transport tar sands gook, ways will be developed to extract more and more. When full accounting is done of emissions from tar sands oil, its use is equivalent to burning coal to power your automobile. This is on top of the grotesque regional tar sands destruction.—Hansen: Norway, Canada, the United States, and the Tar Sands (PDF)After publishing that I somehow don't want to do anything at all.