Mr. Musk is fundamentally a creature of Silicon Valley, a scene that initiated an entire revolution in power dressing. The young masters of that universe dressed down to show that they were members of a new elite — one that refused to dress like the grown-ups they were about to topple. It was the defeat of the suit by the T-shirt.

Publicly insulting one of your biggest customers is not taught in business school, but Elon Musk is not one to let convention get in the way of a good flame war.

President Donald Trump acknowledged arguments between his Cabinet members and Elon Musk but downplayed the friction after a verbal scuffle reportedly broke out between leading members of his administration and his billionaire adviser.