When someone in power silences someone else's speech or expression, then it's correctly a form of censorship, like what management did with r/fatpeoplehate. When the owners, creators or moderators of their own speech or expressions stop producing that content as what many subreddits did in response to r/iama suspending operations, purportedly not out of protest but out of a lack of understanding of a current situation, then it's protest. Censorship is a top-down use of power to silence a majority. Protest is a middle-up form of power to inconvenience a majority to apply pressure to the power holders. They aren't the same.