I mean, I kinda feel like this is a way to effectively protest, because even if they can heavy handedly force you to shut up, you can at least force them to actually do that. The more visibly reddit tries to stamp out dissent, the more people will notice them doing that, and the more upset those people will be. Unlike the irl equivalent, there are few stakes for most people in being involved in this kind of digital protest. At the worst, you get banned there and move somewhere else, which you probably were going to eventually do anyway if youre angry enough to protest reddit like this.

Doing things that force reddit's hand, like making subs nsfw, harms them in some way no matter what: either they do nothing, and lose ad revenue and potentially anger people who just wanted their subs to be what they were, or they capitulate, losing them whatever they wanted to do in the first place and showing precedent for the future, or they try to force things back to normal, and fuel the anger against them even further due to people having feeling restricted. It might not kill the site (even digg and tumblr and such still exist, its very hard for a sufficiently big social site to actually die completely), but it can erode its userbase and grow that of competitors, which reduces the potential revenue the site can make.