Musk likes freedom of speech because he can use it to justify his behaviour, and as a cudgel to silence his critics. It's sort of similar to "think of the children" in that respect. "I'm doing it for the children and you couldn't possibly be against the children, right?" Likewise, Musk proclaims he's doing it for freedom of speech and no one could possibly be against that, could they? Even though it's really just about him.
I suspect he approaches pretty much everything that way. It's either useful to him, or it's 'bad'