Frequent visitors will know, one of my favorite sites is Inhabitat, a green-focused blog with a lot of interesting stories and pictures.  They also run "green news stories", and this one caught my eye: Obama's veto on Keystone pipeline will likely hold.  I was moved to comment:

"Hi could you please explain to your readers why opposing the Keystone Pipeline is good for the environment?

I’m a serious environmentalist but I’m puzzled by other environmentalists' opposition to this project.

In my view, the pipeline is more environmentally friendly than the alternative means of transporting oil from Alberta to Texas. Perhaps not transporting the oil at all would be preferred, but that’s not on the table. We might as well pick the best way to move the oil.

This seems similar to the equally puzzling opposition that some environmentalists have to nuclear power generation. Perhaps not generating power at all would be preferred, but that’s not going to happen, so if power is going to be generated at all let’s pick the cleanest way to do it.

So what's the answer?  Is this another case, like nuclear power, where environmentalists are on the wrong side of a trade-off, or is there another point of view?