No, that's a very indirect impact to any one individual's working conditions.
FWIW, I think firing the organizers is an overreaction and that it would be in SpaceX's best interest to muzzle Elon, but it's hard to conjure up a legal argument that they can't do it. And you'll notice that the company's statement said nothing about the content of the letter, only that it's inappropriate to organize it with company resources and on company time.
Considering how simple-minded and toxic work-cancer employees are, and how harmful and corrupt a union can be; it is no surprise that Musk is 3 steps ahead of them.
FWIW, I think firing the organizers is an overreaction and that it would be in SpaceX's best interest to muzzle Elon, but it's hard to conjure up a legal argument that they can't do it. And you'll notice that the company's statement said nothing about the content of the letter, only that it's inappropriate to organize it with company resources and on company time.