This argument, regardless of its factual correctness regarding the impact on Reddit, is an argument of helplessness - it argues there is no point in acting, because nothing will be achieved.
Sometimes you have to act, even if it will have no effect, because it is the right thing to do, where our sense of moral indignation is so great we are motivated to act regardless of the overall outcome or what we may or may not reasonable expect to achieve.
It simply points out what the ground rules are, if you want to make a point then you can do that but it won't amount to much if it doesn't lead to results.
There are actions that would be much more likely to result in a response, the mods are clearly engaging in a balancing act rather than a principled stance and I predict that if they stay this course they will simply be supplanted by more pliable individuals. A credible threat requires some actual work and preparation, not just the clicking of a link that another party controls anyway.
Sometimes you have to act, even if it will have no effect, because it is the right thing to do, where our sense of moral indignation is so great we are motivated to act regardless of the overall outcome or what we may or may not reasonable expect to achieve.