I haven't done enough reading into the whole pipeline situation to have an opinion on it yet, so don't take this to mean anything in that regard.

Just to play devil's advocate to your point about reducing demand... I think pro-environment people's real goal is to reduce absolute usage rather than specifically demand. Yes, reducing demand does lead to reduced usage (and is the ideal solution), but so does decreasing supply or otherwise making the resource hard/expensive to obtain. This is part of the reasoning behind carbon taxes as well: make polluting more expensive reduces how much it happens without actually having to drive down demand.

Again, not to say this necessarily what's going on with the pipeline situation (I don't know), but this is certainly a common way of thinking that may help explain some people's actions.