Canadian Culture War: Québec vs Alberta
There's this big issue between Québec and Alberta (2 Canadian provinces) where Alberta wants to export its tar sand oil and Québec doesn't like to think about oil. It's a big issue to the extent that a Canadian inter-province feud is a "big issue" but I digress. Anyway, there's been a few projects proposed over the years to extend a pipeline all the way to the east coast which Québec consistently opposes (it's arguably one reason why Canadian Conservatives won the popular vote but got few seats to show for it in the federal elections, last month).
The point of the story is that someone once responded to a claim that this development would be good, economically, for Québec, with a response to the effect that such a project would create a whole ecosystem around itself, with jobs, expertise and everything that comes with it. Such an ecosystem would be hard to take apart (and obviously people in it would resist this taking apart) yet we know (or at least Québécois believe) this will eventually need to happen as we move towards more sustainable energy. This whole tearing down part needs to be factored into the calculus too.
This idea is essentially inertia. Just like in physics. Just like you can't create a wave that'll be strong enough to break some strong barrier but stop right after doing so (it'll break a lot of things behind that barrier before it stops). Except inertia is probably a bad analogy because human systems are not made of inert mass particles but of dynamic human particles. It's perhaps more akin to trying to start a fire in a packed forest to burn down a single elder tree. The fire doesn't have just inertia, it can feed on itself and grow faster as it gets bigger.
This story is an analogy to your needle pushing idea. Some people want to push in a given direction using whatever means necessary (similar to trying to remove a single tree using fire) and they'll keep contributing to it until they feel the goal is achieved (the tree is reduced to ashes), at which point they'll, presumably, start pushing the other way. Internally, this probably feels noble and all and obviously if nobody actually realizes how large the fire will be by the time the one tree is burned down, one can't impute their intentions for the consequences, only their idiocy.
But that's only part of the answer. The truth is that we don't know anyone's intentions. If some number of people claim to only want to burn the one tree and apologize after burning the whole forest, how do we tell which of them are genuine if a bit dumb and which are cleverly lying (which is to say actually wanting to burn the forest all along and saw the former as the perfect means to that end)? This is of course a general point about any movement but the sort of "we care about the direction more than the goal" needle pushing tactic you describe is particularly vulnerable to being used in this fashion.