The letter comes two days after Musk tweeted an unfounded and disparaging claim about Vernon Unsworth, an expert caver who participated in the rescue mission that saved 12 boys and their soccer coach who spent almost three weeks trapped in a flooded cave in Thailand.
The SpaceX chief executive officer labelled Vernon Unsworth, 63, a "pedo guy" after the diver dismissed his offer of a submarine for the rescue as a "publicity stunt" during a media interview on Sunday.
The volume of cancellation announcements on Twitter put Musk on defense, who issued a series of tweets.
The accusation and reaction took some attention away from a different social media flurry on Saturday, when Musk took to Twitter to explain why he donated money to the Republican Party - specifically, $38,900 to a Republican political action committee called Protect the House.
Unsworth responds, "He can stick his submarine where it hurts", before flashing a long toothy grin.
Unsworth's wife told Reuters on Monday that her husband was returning to Britain on July 19, where he will speak to lawyers.
"I do not actually see the checks (changed that policy today)", Musk said in one.
Unsworth said he had saved copies of Musk's tweets and believed that the businessman had "lost the plot", adding: "I have a lot of support from people around the world astonished by his unfounded comments".
Mr Unsworth lives in Chiang Rai.
Mr Chowdhry said that like other important innovators, Mr Musk has zero tolerance for any distractions from his goals, even if he lacks the public relations skills of most CEOs, and that within five to 10 years, Tesla's innovations will be more appreciated. "I will attempt to be better at this", Musk said.
Unsworth told AFP on Monday he had not reviewed the tweets in full and had only heard about them.
"He should focus on his profession", Zhao said, adding that if Musk wanted to help these kinds of causes, he should have a separate charity organization. "It's very much upset my daughter", the caver said, his voice breaking. "I should probably say nothing more often".
He said he felt sorry that the squabble with Musk had detracted from the successful end to the rescue mission.