The American Civil Liberties Union filed a lawsuit Wednesday to defend Milo Yiannopoulos’ freedom of speech.

The ACLU published two articles explaining its decision to fight on behalf of the conservative firebrand against the Washington Metropolitan Area Transit Authority’s restrictions on controversial advertising. Ads for Yiannopoulos’ new book, “Dangerous,” were initially posted in Metro stations and subway cars, but were later removed due over complaints from outraged riders.

The city-funded transit service claims that Yiannopoulos’ ads violated the policies it relied on to reject ads from three other organizations, including the ACLU.

In addition to defending itself and Yiannopoulos’ corporate entity Milo Worldwide LLC, the ACLU named two additional plaintiffs — Carafem, a healthcare network that specializes in getting women access to birth control and abortion medication; and the animal rights organization PETA.

All four organizations have little in common, but ACLU states that their differences “powerfully illustrate the indivisibility of the First Amendment.”

“Our free speech rights rise and fall together – whether left, right, pro-choice, anti-choice, vegan, carnivore, or none of the above,” the ACLU wrote.

“Here at the ACLU, we vehemently disagree with Mr. Yiannopoulos’ views. We work hard, every day, with the very communities he targets, to fight for equal rights and dignity for all,” wrote ACLU director James Esseks in a letter explaining the decision. “We recognize that his words cause grievous pain to many individuals, their families, and their loved ones. Speech like his hurts.”

“Yet even though we know how wrong-headed Mr. Yiannopoulos’ speech is, the ACLU today filed a lawsuit to defend his free speech rights,” he continued. “We did not take this decision lightly. We understand the pain caused by Mr. Yiannopoulos’ views. We also understand the importance of the principles we seek to defend.”

In other words, the ACLU does not agree with anything Yiannopoulos says, but will defend to the death his right to say it. Its decision is comparable to the defense of a variety of unpopular entities, including the Ku Klux Klan, the American Nazis, and the Nation of Islam.

“The constitutional principle here, of course, is that government can’t censor our speech just because it doesn’t like what we say,” wrote Esseks. “But we’re not representing Mr. Yiannopoulos just out of an abstract principle. We’re also representing him because free speech is crucial to progress in civil rights movements.”

“Without free speech protections, all civil rights advocacy could be shut down by the people in power, precisely because government doesn’t agree with the ideas activists advance. That was true of the civil rights fights of the past, it’s true of the movements facing pitched battles today, and it will be true of the movements of the future that are still striving to be heard.”

Esseks cited a variety of cases in which the ACLU stepped up to defend LGBT and the rights of minorities, and added that it was important to fight against censorship as it is “part of how we ensure that the voices of the marginalized do not disappear from public view.”

Ian Miles Cheong is a journalist and outspoken media critic. You can reach him through social media at @stillgray on Twitter and on Facebook.