Re: so when I go to SpaceX/Tesla/Tweetter/Boring HQ
...and I see (as usual) that EM is not at his office, do I have, as a stockholder of these companies, the right to ask for his immediate dismissal with extreme prejudice?
Yes (you might need to clarify the 'with extreme prejudice' bit). You have that right even if you're not a stockholder. Perhaps you could even post your demand on Twitter?