Twitter suspended the account of David Neiwert, a reporter for Daily Kos and author of the book Alt-America, on Tuesday, making him the latest journalist covering white supremacists and the far right to be hit with a temporary ban.

Neiwert said in a phone interview he was banned because the top image on his Twitter profile included an illustration from his book cover, which featured Ku Klux Klan hoods atop a series of stars from the American flag.

Twitter put a notice on his suspended page, reading: “@DavidNeiwert's account is temporarily unavailable because it violates the Twitter Media Policy.” The company declined to comment specifically on Neiwert’s suspension, but its publicly available “sensitive media policy” includes rules prohibiting users from displaying “symbols historically associated with hate groups” in profile or header images.

The type of ban likely means that Neiwert could change the image on his profile and be reinstated—but he said he is refusing to do so “on principle.”

Neiwert shared with The Daily Beast the appeal he sent to Twitter:

“My account was suspended because of the photo of the cover of my book in my profile. This book, 'Alt-America,' is a history of the rise of the radical right in the United States over the past 30 years. It naturally has an illustration featuring KKK hoods because that is its subject. I am one of the nation's leading experts on this subject, and it is insane that you would suspend my account because of this photo. I refuse to remove it on principle.”

Alt-America: The Rise of the Radical Right in the Age of Trump was published in 2017 and chronicled the trajectory of far-right and white supremacist groups since the 1990s. Neiwert had used the cover illustration on his Twitter profile without trouble since the book was published.

Neiwert speculated that he had become the target of trolls whose accounts he has flagged to Twitter recently.

“I’ve been reporting people who are obviously hate mongers, who came into my account, and probably some of them are retaliating,” he said.

Neiwert is the latest journalist to be suspended under policies purportedly designed to combat hate.

In April, Michael Edison Hayden, a senior investigative reporter with the Southern Poverty Law Center, was locked out of his account for a tweet about a specific symbol used by white nationalist groups. Twitter eventually reversed course and sent Hayden an apology.

Similarly, recent policy changes by YouTube to remove content by white supremacists and neo-Nazis have also wound up hurting journalists, educators and researchers whose work touches on such topics.

“If they’re not even able to distinguish anti-extremist content from extremist content, they have a serious problem,“ Neiwert said.