It's worth noting that journalism as a profession has a problem with letting itself become political. Seems like for a journalism association to be effective in these cases, it must insist on the impartiality that most institutions seem to be finding too difficult lately.
Unions might not be a very good fit either. They do have fists and I would expect a good union to put a fight for any member that got laid off, even if the union leadership finds that defending the person is a burden. But the union probably would not care about impartiality of reporting or help publish a particular view.
But this does look like an almost perfect case for the freedom of speech defenders. I do not know why are they not helping. My only guess is that they are used to fighting the government or megacorps and have no idea how to help in this setup. But this is just a random guess.
This and the below
>journalism as a profession has a problem with letting itself become political
Unions are by definition political, so that wouldn't solve the problem you describe.