A group of digital advertising and marketing organizations has come together today to condemn Apple for what the coalition says is a “unilateral and heavy-handed approach” to user privacy on Mac. The group fears that Apple, which has started taking more extreme measures to reduce ad tracking on both the mobile and now desktop versions of Safari, is unfairly exercising its muscle in a way that could snuff out an entire segment of the ad industry.

The open letter, published this morning by six leading advertising trade groups, is in response to a new macOS feature Apple calls Intelligent Tracking Prevention, or ITP. Introduced back at WWDC in June, ITP uses machine learning algorithms to identify tracking behavior on the company’s Safari browser, like the presence of persistent cookies from third-party ad networks, and imposes a strict 24-hour time limit on those tracking tools’ lifespans. Apple unveiled the new feature by saying, “It’s not about blocking ads, but your privacy is protected.”

Advertisers are worried Apple’s changes would make Facebook and Google more powerful

Apple’s commitment to user privacy is notable, especially in an era of free web services and ever-increasing ad targeting and tracking. However, advertising groups fear the decision would decimate their businesses at a time when Facebook and Google already gobble up more than 90 percent of every new ad dollar spent on the web. Because of Facebook and Google’s deep pervasiveness on the web, users often stay logged into each company’s services all day long, and visit each one’s primary websites at least once a day, if not more. That renders Apple’s 24-hour ad-tracking prevention measures ineffective for those two web behemoths, while mainly harming smaller advertising companies like Adroll and Criteo that manage cookies in the background of thousands of websites.

“Apple believes that people have a right to privacy — Safari was the first browser to block third-party cookies by default and Intelligent Tracking Prevention is a more advanced method for protecting user privacy,” Apple said in a statement given to The Verge. “Ad tracking technology has become so pervasive that it is possible for ad tracking companies to recreate the majority of a person's web browsing history.”

Apple is talking here about a distinction between first-party and third-party cookies, with ITP targeting the latter. “This information is collected without permission and is used for ad re-targeting, which is how ads follow people around the Internet,” the company adds. “The new Intelligent Tracking Prevention feature detects and eliminates cookies and other data used for this cross-site tracking, which means it helps keep a person's browsing private. The feature does not block ads or interfere with legitimate tracking on the sites that people actually click on and visit. Cookies for sites that you interact with function as designed, and ads placed by web publishers will appear normally.”

Additionally, the advertisers’ defense here isn’t all that convincing, beyond the outright fear of total decimation at the hands of three of the world’s most valuable and influential corporations. “Blocking cookies in this manner will drive a wedge between brands and their customers, and it will make advertising more generic and less timely and useful,” the open letter reads. “Put simply, machine-driven cookie choices do not represent user choice; they represent browser-manufacturer choice.” The group says Apple is overriding user choice by imposing its own set of “opaque and arbitrary” standards.

Advertisers are effectively trying to argue that users should have a choice whether or not they’re tracked across websites through browser cookie preferences, as an extension of the choice to be served more direct and useful ads. It’s a murky situation, to say the least, because it pits the often vilified web ad industry against the very real and justified concern that Silicon Valley’s largest companies now represent unprecedented monopolies capable of crushing competition.

It’s unclear how this contentious showdown will play out. But what we do know is that while Apple sees protecting user privacy as a strong differentiator and a great PR move, it doesn’t appear to care too much about emboldening Facebook and Google in what is already a dangerously lopsided market, one that will likely see a further consolidation of market power in the hands of the tech industry’s biggest titans.

Update at 8:00PM ET, 9/15: Added statement from Apple.