The arrest of the CEO of Backpage, an adult classifieds website, has drawn criticism from sex workers and first amendment advocates who argue that the prosecution violates free speech protections and could do more harm than good.

The top prosecutors in California and Texas announced on Thursday that authorities had arrested Backpage executive Carl Ferrer on felony pimping charges, alleging that his website profits from the “trafficking and exploitation of vulnerable victims” when it collects fees for “escort” ads.

But legal experts said that online platforms like Backpage.com cannot be held liable for the actions of their users and that third-party sites are protected by free speech internet laws.

The charges have also sparked outrage among sex worker activists who argue that Backpage is a safe way for them to advertise services and vet clients, and that without it, some would be working on the streets, which can be significantly more dangerous.

“This has nothing to do with people being exploited. It’s a political ploy,” said Kristen DiAngelo, executive director of the Sex Workers Outreach Project of Sacramento.

Under Backpage’s “adult” section, people can advertise a range of services, including escorts and fetishes. According to sex worker groups, consenting adults use the platform for legal activities such as massages, as well as illegal paid sexual encounters.

But California’s attorney general, Kamala Harris, who is running for US Senate, alleged that “many” ads for prostitution involve sex trafficking victims, including minors. She claimed that Ferrer, along with shareholders Michael Lacey and James Larkin, have profited from these crimes and that Backpage is “essentially operating as an online brothel”. All three men are accused of conspiracy to commit pimping.

David Greene, civil liberties director for the Electronic Frontier Foundation, said the law is clear that “those who provide internet services cannot be considered publishers of content that they didn’t create themselves”.

Section 230 of the Communications Decency Act, a law that has had a profound impact on the internet, outlines these protections. The act, for example, has established that Yelp is not responsible for negative reviews and that eBay is not liable when people sell counterfeit items.

Airbnb, the home-sharing startup, has also argued that the law shields the tech platform when users violate local housing laws.

Backpage has repeatedly won legal victories based on free speech arguments.

“You can think that child trafficking is a horrible thing … and still think that prosecutors have overreached by going after the CEO of a classified advertising service,” Greene said.

DiAngelo argued that targeting a web platform was a “slippery slope” and that prosecutors could go after landlords of buildings where sex work may be occurring or newspapers that print ads for services that turn out to be illegal.

Spokespeople for the Texas attorney general, Ken Paxton, and Harris declined to comment.

In an email to the Guardian, Liz McDougall, Backpage’s lawyer, said the arrest “is an election-year stunt, not a good-faith action by law enforcement” and noted that the company has policies against “illegal content” and removes ads when contacted by police.

“The actions of the California and Texas attorneys general are flatly illegal,” she wrote, adding that “Backpage.com will take all steps necessary to end this frivolous prosecution.”

Legal arguments aside, activists have argued that targeting Backpage is a misguided approach that conflates trafficking with adult sex work. Critics also say that closing the site won’t eliminate the exploitation, but simply move it further to the margins.

Maxine Doogan, president of the Erotic Service Provider Legal, Educational and Research Project, said that Backpage allows sex workers to control their own businesses online without having to rely on pimps or work in the streets. Workers also use the site to warn each other about dangerous or violent clients, she said, noting one woman who was robbed by a man and then posted his name and photo on the site.

Often, she said, that can be the only way for workers to protect themselves since reporting to police can get them arrested for prostitution.

Doogan, who is based in California, noted that the Backpage criminal charges aren’t even about trafficking and accused Harris of using the case to bolster her campaign. “The underpinnings of the pimping laws is the criminalization of prostitution.”

Kimberlee Cline, a sex worker based in Sacramento, said Backpage allows her to get references from other workers about whether a certain client is safe, she said. “It’s absolutely vital.”

Cline added: “The saddest part of all of this is the amount of time and energy and resources they are spending that are supposedly intended to protect real victims of sexual exploitation … These efforts are only about arresting sex workers, not stopping human trafficking.”

After authorities shut down a similar adult services site called MyRedbook.com, according to DiAngelo, her organization surveyed 44 workers and found that 18% had transitioned to the street and subsequently experienced rape, arrest or both.

“If they keep marginalizing the people who are in the sex trade … there’s no way they can stand up and say, ‘We’re doing this to save you,’” DiAngelo said, noting that the state should instead invest in social services for victims.

Some activists have also argued that traffickers can be exposed and arrested through Backpage.

“Why would the government want to shut down a resource that they can use to actually go after people who are selling minors?” said Norma Jean Almodovar, a California sex worker activist.

Critics said that if California prosecutors were serious about supporting victims, they would have done a much better job handling the recent scandal in which more than a dozen police officers throughout the Bay Area have been accused of exploiting and paying a teenager for sex.

While the state has aggressively targeted the Backpage CEO, many of the officers in the Bay Area case have avoided serious consequences.

“You’ve got cops that are wildly abusing sex workers and nothing happens to them,” Almodovar said. “That says you really don’t care about us at all.”