I had a similar interpretation. I read it very much as being about working conditions (in which case the letter would be protected by labor law), and was surprised to see the twitter behavior as the primary action item, citing working conditions as action items 2 and 3.
Not a lawyer, but the primary action point being about the twitter behavior seems to significantly cast doubt upon what would've otherwise seemingly been a slam dunk labor law/retaliation violation case.
Elon is toxic and is hurting the business and their personal incomes, they have every right to criticize the merging of Elons political ambition with the space mission. Elon is the main thing holding back Tesla and Space-X.
I think you have it the wrong way around. Elon's space mission is a political mission. He wants to be the first to colonize Mars. Heck it's even a personal mission of his. SpaceX is nothing without him - I'd go so far as to say Elon Musk is SpaceX.
Publicly address and condemn Elon’s harmful Twitter behavior. SpaceX must swiftly and explicitly separate itself from Elon’s personal brand.
This is the spirit of their demands and they made it personal.