If you're opposed on principle to someone being punished for a speech act (i.e. because "words are not violence", etc) then you oppose someone being fired for a speech act, whether the firer has the legal right to do it or not.
Everyone who participated in "cancel culture" against right wingers had a right to do what they were doing, but for free speech supporters it was still wrong on principle to do it.
So, yeah, it's always "the employers call". But if we're talking about free speech, the employers call can be ethically wrong-- i.e. in exactly the way the right was saying the suppression of certain forms of language was wrong about 5 mins before they got the power to start threatening people's use of language.
Should Musk make good on his promise to pay the legal bills of someone who "gets into trouble at work" for tweeting a celebration of Charlie Kirk's murder, or is this somehow different from someone getting fired for saying the N-word?
You're copping out on this and you know it.