Truth is, arguing with the boss in the market square is not in every sense a protected sort of speech.
It's only because Musk himself advertises his credentials as a free speech advocate that there's a problem.
If he ever thinks about it, he'll realise the rules about speech are nuanced. The free speech "right" is in relation to government. There are all sorts of rules about other kinds of speech. And within any organisation built around a hierarchy, there are ways of getting yourself fired by telling things as they appear to be.
What Musk seems to mean by free speech is that HE wants to be able to say what he wants without consequence. But his boss is the customer/advertiser. And they are putting the bridle on him, just as he is putting it on his employees.