The technology company Salesforce is facing mounting pressure to cancel its contract with US Customs and Border Protection (CBP), with protests targeting its CEO, Marc Benioff, on Tuesday.

Emails from Benioff, recently obtained by the Guardian, have also raised questions about the billionaire founder’s response to the backlash against his cloud computing company. CBP, a law enforcement agency that carries out Donald Trump’s anti-immigrant agenda, began using Salesforce products this year to “manage border activities” and “modernize its recruiting process”.

At the height of the family separation crisis over the summer, Benioff contacted a leading not-for-profit group to discuss the growing opposition to his firm’s contract – and then backed out of a call at the last minute, saying he was busy with vacation activities, the emails showed.

“I am sorry I’m actually scuba diving right now,” Benioff wrote to Jonathan Ryan, the executive director of the Refugee and Immigrant Center for Education and Legal Services (Raices) on 23 July, the day of their scheduled call.

“The first thought in my mind … was, ‘What is this guy thinking?’” Ryan said in a recent interview. “I’m managing the crisis of my lifetime, which is nothing compared to the collective crisis of all the people we are trying to help … It’s one thing to be too busy. It’s another thing to be too busy because you’re scuba diving.”

Raices, a Texas-based organization that provides services to refugee and immigrant families, entered the national spotlight after the Trump administration’s “zero-tolerance policy” led to family separations at the border. The practice was widely criticized as “inhumane” and “horrific”, and Raices raised millions to advocate for detained families.

But in July, Raices publicly rejected a $250,000 donation from Salesforce, citing concerns about the the CBP contract.

As protests continued this week at the company’s annual Dreamforce conference in San Francisco, Ryan discussed his ongoing concerns with Salesforce and his communications with Benioff after Raices turned away his donation.

After reading his first email, Ryan said it appeared the CEO did not understand the gravity of the situation: “As dark as the times were, and as impolite as the brush-off was, I still had to smile at that ludicrous image in my mind of a billionaire in cahoots with a government that is actively running the lives of children, and he’s … scuba diving with his family.”

Benioff isn’t shy about divulging his leisure activities. He recently gave an interview to the New York Times while he said he was getting a massage.

The two connected by phone a week after Benioff asked to reschedule. Ryan said he felt Benioff was “largely undereducated” on the facts of the crisis and on the functions of CBP and border patrol.

“It was a surprise to me considering how far into the debate we were,” said Ryan, adding that Benioff defended the relationship and tried to downplay the significance of the contract. The CEO, who has a reputation of being a progressive “social activist”, also did not directly answer his question about whether Salesforce would commit to severing ties after the contract expired, according to Ryan.

Benioff sent an email after the call saying he would like to meet in person, but had not followed up since, Ryan said.

Salesforce representatives declined to comment on Benioff’s communications with Raices, saying only that the CEO had “personally engaged with several Salesforce employees, customers and non-profit groups on this topic”.

In June, concerned Salesforce employees wrote a letter to the CEO saying the company should re-examine its contract and “speak out” against CBP, adding, “Given the inhuman separation from their parents currently taking place at the border, we believe that our core value of Equality is at stake.” Benioff, who recently bought Time magazine with his wife Lynne, has responded to criticism by saying the company doesn’t work with CBP “regarding separation of families”.

But opponents have argued that by providing technology to “recruit and support new agents” and “drive efficiencies around US border activities”, Salesforce is complicit in a humanitarian crisis perpetuated by the US government.

“The inhuman practices that are in full effect along our border today are all continuing to be supported by the Salesforce platform,” said Ryan. “It is what makes their operations more brutally efficient and violently effective.”

Activists showed up at the center of the busy Dreamforce conference on Tuesday morning with a 14ft-tall cage that said “Detention center powered by Salesforce”, with signs reading: “Caging children is a crime not a business model.”

“You are complicit!” one activist shouted at conference attendees, who largely ignored the demonstration. Some passersby who weren’t attending the events shouted messages of support, including, “No CBP!” and “Put Trump in that cage!”

Tech companies have increasingly come under fire for their role in assisting the Trump administration.

Ryan said the Salesforce contract and the company’s ongoing defense was reminiscent of IBM’s work supplying the Nazis with technology used to help transport people to concentration camps.

If Salesforce ended its contract, Raices would accept its donation, said Ryan, adding that the move would encourage other companies to follow suit.

“It would be heard by the people who have been the victims of these instruments of violence and would put Salesforce in a position to be in the history books as drawing a line in the sand for humanity,” he said.

The protests follow a string of devastating news stories about CBP and immigration enforcement. Earlier this month, a border patrol agent was charged with murdering four women and labeled a “serial killer” by police. Other CBP agents have been accused of sexually assaulting teen girls and fellow officers while on duty. A recent report found that the number of detained migrant children has soared to the highest ever recorded.

Ending the Salesforce contract with CBP could disrupt the hiring of agents, said Jacinta Gonzalez, an organizer with Mijente.

“As we look at this administration’s white supremacist agenda … it’s important to track companies that are making millions if not billions of dollars from the suffering of migrant communities,” she said.

Jelani Drew, a campaigner at Fight for the Future, added: “Technology has the potential to enable human rights abuses at a mass scale – or stop them.”

Salesforce did not respond to questions about the future of the CBP contract.

In a recent earnings call, Benioff spoke of his commitment to the “ethical and humane use of technology”, saying: “We have to make sure that technology strengthens our societies instead of weakening them.”

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