Honestly, the pipeline isn't really the problem. Pipelines are the least terrible way to transport oil, creating by far the least CO2, and even ruining the least amount of land and water with spills, simply because trucks and trains crash more.
The REAL problem is that the pipeline makes it profitable to exploit the oilsands, which is basically the preteen child labor of energy. It is horrible for the environment to extract, horrible for the planet to prepare for shipping, terrible to refine and after all that, it's still crude oil.