What is your evidence of him being unstable?
I have tons of respect for what Musk has done with Tesla and SpaceX, but it's undeniable that some of his tweets should not have been sent. And while I generally appreciate weirdos, he's a bit much sometimes.
I mean you want to call him a asshole fine, but doesn't mean he is unstable.
If everybody that gets on fight on twitter or is sending tweets that shouldn't be sent is considers 'unstable' then most people on twitter are unstable.