How should a corporate board respond to a CEO publicly insulting and shaming a sitting president? It’s not a question that most need to consider, since few chief executives dare to directly criticize the White House.

As Elon Musk and Donald Trump take jabs at each other online, their respective businesses are plummeting in value.

Though their war of words on social media has slowed, the world’s richest man and the U.S. president isn’t over yet as Trump vows to sell his Tesla.