A longtime Fox News commentator on Tuesday let the network have it in a scathing letter to colleagues announcing his departure.

In an email to Fox News staff, first obtained by BuzzFeed News, strategic analyst Ret. Lt. Col. Ralph Peters claimed he decided not to renew his contract earlier this month because of how “ashamed” he is of Fox.

Peters attributed his decision to Fox’s defense of President Trump amid alleged Russian collusion in the 2016 presidential election, declaring that the network was increasingly “wittingly harming our system of government for profit.”

“Fox News is assaulting our constitutional order and the rule of law, while fostering corrosive and unjustified paranoia among viewers,” he wrote in the email. “Over my decade with Fox, I long was proud of the association. Now I am ashamed.”

He continued: “Fox has degenerated from providing a legitimate and much-needed outlet for conservative voices to a mere propaganda machine for a destructive and ethically ruinous administration.”

In a statement, Fox News said: “Ralph Peters is entitled to his opinion despite the fact that he’s choosing to use it as a weapon in order to gain attention. We are extremely proud of our top-rated primetime hosts and all of our opinion programing.”

Amid his anti-Fox missive, however, the retired colonel did make carve-outs for some colleagues.

He exempted the increasingly political Fox Business Network—which The Daily Beast has reported as even more pro-Trump than its sister channel—as well as some hosts and reporters who have “shown courage” by standing up to the “propaganda mouthpiece.”

But for a negative association, Peters singled out Fox’s primetime hosts for repeatedly running block for Trump by dismissing and agitating against federal law enforcement and Special Counsel Robert Mueller’s investigation into Russian meddling in the 2016 election.

“When prime-time hosts—who have never served our country in any capacity—dismiss facts and empirical reality to launch profoundly dishonest assaults on the FBI, the Justice Department, the courts, the intelligence community (in which I served) and, not least, a model public servant and genuine war hero such as Robert Mueller—all the while scaremongering with lurid warnings of ‘deep-state’ machinations—I cannot be part of the same organization, even at a remove,” Peters wrote.

Perhaps ironically, Peters has never been known as one of the network’s moderate or even left-leaning contributors.

In the past, Peters has used his Fox News airtime to bash Muslims and advance extremely hawkish national-security policies. He was infamously suspended by Fox News for two weeks in late 2015 after he described President Obama as “a total pussy” on-air.

And yet he had become increasingly critical of Fox News and the network’s viewers under the Trump administration.

Last month, he acknowledged that his support for gun control in the wake of the Parkland shooting was unpopular with the Fox audience, and said that keeping assault weapons off the street was “a moral issue” that was about “dead children.”

During an interview with Fox News host Tucker Carlson last year, Peters compared the primetime anchor to a Nazi apologist for defending Putin’s actions in Syria.

“You sound like Charles Lindbergh in 1938, saying, ‘Hitler hasn’t attacked us,’” Peters said.