Musk on Saturday called Michael Brune, the Sierra Club’s executive director, and asked that he make public more than $6 million in contributions to the group that had been anonymous, Brune wrote in the email. Musk also enlisted Brune to vouch for him on Twitter to quell a firestorm over the billionaire’s $38,900 contribution to a committee that benefits congressional Republicans including House Majority Leader Kevin McCarthy.

Brune is now dealing with blow-back within his own organization for complying with Musk’s requests. Two posts from his personal account and one sent from the Sierra Club’s Twitter handle that were laudatory of Tesla’s chief executive officer and his commitment to fighting climate change rankled some Sierra Club staff. They objected to Brune’s defense of an executive who funds Republicans and has bashed the United Auto Workers.

We're proud of Elon's support of our work. — and, we will continue vigorously fighting the climate deniers in the GOP. But Elon's innovation and leadership on climate cannot be denied.

— Michael Brune (@bruneski) July 15, 2018

“I appreciate the concerns that I’ve seen online and in email that the tweets may be at odds with our support for workers’ rights and defeating the GOP agenda across the country,” Brune wrote in the email to his staff on Tuesday. “I don’t agree, but I see the risk and understand the concerns. Musk has made unhelpful anti-union statements and Tesla’s labor practices are also cause for concern, so I take your comments seriously.”

A representative for Sierra Club declined to comment. A spokesperson for Musk said in an emailed statement that he is “committed to backing the Sierra Club in its fight for clean energy and recently asked them to make his support public to reaffirm the sincerity of his commitment.”

“Elon has spent most of his career fighting to prevent climate change and protect the environment,” the spokesperson said in the statement. “Almost every major carmaker in the world is accelerating development of electric cars primarily because of what Elon and his team have achieved with Tesla. He has also made significant philanthropic contributions to organizations seeking to end the use of fossil fuels, including $6 million to the Sierra Club.”

Musk, 47, defended himself on Saturday in a series of tweets by denying that he’s a top donor to the GOP or any political party. He also wrote that his contribution to a committee known as Protect the House was about 0.5% of what he donated to the Sierra Club and said this was “a reasonable amount to maintain an open dialogue.”

In another post, he said he donated to the PAC that benefits Republicans “so that they are willing to listen when I call to object about issues that negatively affect humanity.”

Laudatory Tweets

Brune joined the fray, tweeting from his personal account over the weekend that Musk “has spent his career focused on tackling the climate crisis & advancing clean energy” and that the Sierra Club is “ proud of Elon’s support of our work.”

“There have got to be better topics of debate than whether @elonmusk is committed to climate action,” Brune wrote in the tweet posted from the Sierra Club’s official account. Musk quoted that post and wrote back in a post that he pinned to the top of his feed: “Thank you for fighting climate change. This affects every living creature on Earth.”

In the email to Sierra Club staff, Brune said that it was Musk’s right to request that his previously anonymous donations be made public, and said the group would have granted that request to any donor.

Musk “asked for some help via Twitter, not about the PAC donation but to buttress the criticism that his commitment to ending fossil fuels was fake,” Brune wrote in the email. “I agreed.”

Unionizing Effort

Tesla’s assembly plant in Fremont, California, has been the target of an organizing campaign by the UAW. Brune is a co-chair of the BlueGreen alliance, a partnership between unions and environmental advocates. He’s spoken at the UAW’s convention and lent support to campaigns including the union’s attempt to organize a Nissan Motor factory in Mississippi.

In a complaint now pending before an administrative law judge, a regional director of the National Labor Relations Board has alleged that Tesla management violated federal labor law by restricting employees from organizing activities, trying to stop employees from discussing safety issues, and retaliating against pro-union workers.

Tesla has said the claims have no merit. At the opening of the hearing on them in June, the electric-car maker’s attorney said that the trial was “an infomercial in an effort to place Mr. Musk and the company in a negative light.”

Controversy over Musk’s political spending was overshadowed on Sunday by tweets attacking a British cave explorer who criticized efforts by the CEO and his rocket company Space Exploration Technologies to craft a mini submarine to aid the rescue of 12 boys and their youth soccer team coach in Thailand.

In posts that he later deleted, Musk referred to the man as a pedophile. He has since apologized.