"Arguably that's not a big difference"
For some people it may be a subtle distinction, but it nevertheless a very important one. Software is legally of the same status as speech. Free speech protections in the US constitution mean the law can't compel you to say something you don't believe. Nor as a free citizen or free enterprise, do you have to supply your effort to an action you (or if an enterprise, your board) do not believe in. There is a profoundly important principle that we should seek to preserve, and that is that the government works for the people. At the best of times Politicians are wont to forget that, and it is always bad if they do, so it is always an important to fight to retain the distinction. This action subtly, but significantly tips the balance the wrong way and steps over the line. If the FBI win, the people of America will no longer be able to call themselves free citizens.
Of course many have been saying that for years, but until now those arguments have relied on the notion of psychological enslavement to the government (e,g, sheep like thinking) as distinct from legal enslavement.
BTW, I made this point on the Times editorial about this, in the same tone of voice. My comment was censored.
Also this strange amendment to a NYT article on the subject. Note, not recording there has been an amendment breaks their own strictly enforced editorial guidelines.