Consider the Source
First, I wrote at the beginning of the year, in the context of the Joe Rogan controversy, that tech companies needed to understand that “free speech” was no longer a defense in terms of elite culture; that statement got a lot of pushback, but this seems like confirmation of the thesis: Musk didn’t promise to bring back trolls and hate speech, but he did frame the Twitter acquisition in terms of free speech, and that was interpreted as being about, well, trolls and hate speech.
I think this is confirmation bias (something Ben actually calls out earlier in this article) because I don't think this is showing that "free speech" is a dirty word these days. You need to account for the source and the context of this, which is not a simple matter of advertisers hearing "free speech" and running for the hills. Context matters, and anyone following along with this Musk/Twitter saga knows that Musk wants to bring back a lot of accounts and content that advertisers may not want their ads running next to in your feed.
Also, these companies are unsure what the platform is going to do under Musk's now absolute power, and if you can imagine it, they don't love uncertainty, so pulling back on ad spend seems completely reasonable.
For my part, when I hear Musk say he wants to make Twitter more open to free speech, I don't expect him to want to make it a better place for marginalized groups who deal with harassment because literally nothing he has ever done shows me he's interested in that; he cares about offensive memes. He's allowed to do this, but I and advertisers are also allowed to walk away if we don't like it.
My free speech, your free speech, and Elon's social network's free speech are all allowed, but non of them are allowed to avoid consequences - especially if that consequence is people not wanting to deal with you because they think you're kind of an asshole.