Not that I think Twitter ever was or will be a shining beacon for free speech but I'm not sure impersonating someone to impugn their character qualifies. Sure, you could argue that this is all just parody and it should be obvious that it isn't really Elon Musk making these tweets but the fact of the matter is there will be millions of people who think it is him. A better question might be how equally this policy is enforced. If someone changes their name to Kathy Griffin and tweets stuff to make her look bad (I mean worse if that is possible) then would they be banned?
At the end of the day this is a good thing. Hopefully this will drive more people away from twitter and make for a more competitive social media environment...and maybe even drive a few people to use platforms like Hive.