Earlier quoted context omitted.
What you describe isn’t blackmail. Blackmail is offering the celebrity the chance to keep you from offering the story to the others, in exchange for a fee. If you actually had a setup as you described, all of the news outlets would publish the facts of your story, without paying you anything, because facts aren’t protected by copyright. The only thing you could sell would be an exclusive interview.
So it's an ordering problem? It's only blackmail if I offer to sell my silence before making offers to other parties? So if I have an offer from a movie studio for the rights to my story and then allow the celebrity to make a counter-offer, that's not blackmail? When I said publishing house I meant book publishers like Penguin Random House. I don't know where news outlets come into it.
Whether the medium is a book or a newspaper or a website is legally immaterial. Thinking about the information as news is just useful because no one owns the facts, only their particular descriptions of them.