I agree with the first part. But you can have high standards, call out incompetence and fire people without being an asshole (or without being perceived as one). A good example is Ray Dalio.

The thing is, Elon Musk is emotionally immature. He's extremely thin-skinned and narcissistic. He likes to take revenge. There's a difference between firing someone because it will help the project and doing it because you're angry and it will make you feel good.