When I was at Microsoft we had a type of problem I imagine infests all large corporations, exemplified by a particular group who I used to call the "Dysfunctional Team".
They would show up to meetings with my team with a list of requirements (not requests, naturally), and basically all of them would be 'priority 0'. The scale actually went from one to three, saying something was priority zero was used by some to show how extra specially important that one thing was.
People are often measured against the local minima of their smaller group within the larger organization. They aren't rewarded for making sure that the overall company does the best thing possible, they are rewarded for pushing their local goals and their ability to get them implemented.
Taken to its logical extreme, this involves going to a supposed partner team with every request being a 'pri 0'. Once you notice that they tend to more reliably be implemented, and you know that you're rewarded for getting things done, clearly labeling everything that way makes the most sense.
I watched the premier for a new AMC original series called "Mad Men" yesterday (you can take a minute to stare in awe at that incredible segueway). It looks really good. In the Making Of they mentioned that the head writer and executive producer, who was one of the main guys behind The Sopranos, was very insistent that it be as true to life as possible. That means smoking and drinking constantly and at work, rampant and open racism and sexism, and other things that create a culture shock both in contrast to the United States in the 21st century as well as to someone like me, who was raised in the American West in the 70s and 80s.
The reason that I mashed these two subjects together is to make the point that for Causes, proponents tend to have the same issues that small groups within large organizations in general have. They are also rewarded for how well they push their local goals within the larger setting, not how well they help the larger setting make the right balanced decisions and prioritization.
You see a lot of people who care deeply about something fall into the Pri 0 trap, and the result is similar to how we viewed the Dysfunctional Group. Everything can't possibly be Pri 0, ignore what they're saying and come up with our own prioritization.
As a society we've made huge progress on many of the issues raised by Mad Men. That does not mean the problems are solved, they certainly aren't, but if you look at how far we've come in this country with racism, sexism, etc. both since the 60s and compared to many places around the globe, it is valuable to acknowledge the progress and realize how much better things are than they were or could be.
It also shows how much better things can and hopefully will be as we make more progress in the future on the same issues.
The point I'm trying to make, aside from Mad Men being a good show that's worth checking out, is that the Pri-0ers are not the engine of progress.