"Free speech" isn't a factor on a private company. Just the TOS matters and impersonating people without stating it is a parody has always been against Twitter's TOS. He isn't banning for mocking, he is banning for impersonation.
Which he only started doing after HE was the one impersonated. And its a liufetime ban. Meanwhile, you can spread election lies, covid lies and racsim - and IF you get banned, its not lifetime.
Musk - the guy who once asked Chinese social media censors to block posts critical of his company.