If the letter alleges that Musk directly harassed employees, that would be entirely different. But it doesn't; it merely says that Musks behavior in the public sphere is unpleasant (again, that's fair).
Working Conditions means the conditions under which the work of an employee is performed, including physical or psychological factors.
The things that that letter discusses affects the psychological factors of the work. Committing to making people feel included, defining what toxic behavior will not be accepted, and so on.
Your linked definition includes in working conditions, "...all existing circumstances affecting labor in the workplace." This fits with the definition that I gave - the behaviors that you have to put up with from coworkers affects labor in the workplace.
This is way too reductionist. These aren't just "Musks tweets", they are directives about employee policies that are publicly stated, but not private enforced (because, to the author's criticism, they have no strict definitions). Furthermore they have clear (or at least implied clearly) repercussions: "don't behave they way we want to or you're fired".
> all could be considered about working conditions.
Actually, I think what the author is asking for is clarity about working conditions, not necessarily the working conditions are good/bad - they're just ambiguous.
This is backwards. There are lots of rules out there which I'm sure you dislike. Therefore your dislike of this one is irrelevant.
And I say that despite agreeing with you about how it might be abused. And despite wondering whether the people calling for more diversity and exclusion in this letter may be the kind of people to abuse it that way. Rules are rules, and we should try to apply them fairly, especially when applied to people we dislike.
Maybe those companies shouldn't include statements like this in their corporate filings then:
"The Twitter account @elonmusk is considered an official corporate communication channel."
Especially when Musk is tweeting from it things like changes to remote work policies.
Forcing a trucker to drive 20 hours straight is working conditions. Refusing to install proper lighting in a warehouse is working conditions.
Having a policy saying "don't be an asshole", and then enforcing it in a way that is perceived as unfair, is not working conditions.
If the letter had directly alleged that Musk or other leadership was abusive towards the employees, they would have a case. But just saying "we thing Musk is an asshole, and we have a no-asshole policy" is not protected speech.
Many employment laws just create causes of action for civil litigation. I.e. they define types of harm for which the employee can seek compensation in the courts.
Very specifically for this case, they protect the right of employees to talk to an employer about improving workplace conditions. With or without a union, and with or without any interest in unionization.