The world’s richest man is a fan of free speech, but he also recognizes blatant insubordination when he sees it.

SpaceX CEO Elon Musk appears to have cracked down on a budding mutiny at the groundbreaking company, firing some of the staffers who were behind an open letter to executives that was critical of some of Musk’s “embarrassing” and “distracting” tweets.

The letter begins, “An open letter to the Executives of SpaceX,” and adds:

In light of recent allegations against our CEO and his public disparagement of the situation, we would like to deliver feedback on how these events affect our company’s reputation, and through it, our mission.

Employees across the spectra of gender, ethnicity, seniority, and technical roles have collaborated on this letter. We feel it is imperative to maintain honest and open dialogue with each other to effectively reach our company’s primary goals together: making SpaceX a great place to work for all, and making humans a multiplanetary species.

As SpaceX employees we are expected to challenge established processes, rapidly innovate to solve complex problems as a team, and use failures as learning opportunities. Commitment to these ideals is fundamental to our identity and is core to how we have redefined our industry.

But for all our technical achievements, SpaceX fails to apply these principles to the promotion of diversity, equity, and inclusion with equal priority across the company, resulting in a workplace culture that remains firmly rooted in the status quo.

Individuals and groups of employees at SpaceX have spent significant effort beyond their technical scope to make the company a more inclusive space via conference recruiting, open forums, feedback to leadership, outreach, and more. 

However, we feel an unequal burden to carry this effort as the company has not applied appropriate urgency and resources to the problem in a manner consistent with our approach to critical path technical projects.

To be clear: recent events are not isolated incidents; they are emblematic of a wider culture that underserves many of the people who enable SpaceX’s extraordinary accomplishments. As industry leaders, we bear unique responsibility to address this.

Elon’s behavior in the public sphere is a frequent source of distraction and embarrassment for us, particularly in recent weeks. As our CEO and most prominent spokesperson, Elon is seen as the face of SpaceX—every Tweet that Elon sends is a de facto public statement by the company.

It is critical to make clear to our teams and to our potential talent pool that his messaging does not reflect our work, our mission, or our values.

SpaceX’s current systems and culture do not live up to its stated values, as many employees continue to experience unequal enforcement of our oft-repeated “No A**hole” and “Zero Tolerance” policies. This must change.

The letter went on to demand that executives “publicly address and condemn Elon’s harmful Twitter behavior. SpaceX must swiftly and explicitly separate itself from Elon’s personal brand.”

Also, the letter demanded that “all leadership” be held “equally accountable to making SpaceX a great place to work for everyone” — what many considered a direct reference to Musk.

“Define and uniformly respond to all forms of unacceptable behavior,” the staffers added before concluding this challenge: “Is the culture we are fostering now the one which we aim to bring to Mars and beyond?”

The New York Times reported that the company investigated those behind the letter and some have been dismissed:

SpaceX, the private rocket company, on Thursday fired employees who helped write and distribute an open letter criticizing the behavior of chief executive Elon Musk, said three employees with knowledge of the situation.

By Thursday afternoon, SpaceX had fired some of the letter’s organizers, according to the three employees and an email from Gwynne Shotwell, SpaceX’s president and chief operating officer. In her email, which was obtained by The New York Times, she said the company had investigated and “terminated a number of employees involved” with the letter.