Kelvin Cochran, right, with his attorney, David Cortman, at a Feb. 18 news conference in Atlanta. Photo: Ben Gray/Associated Press

Kelvin Cochran has led a remarkable life by any standard. He was born into a poor family in Shreveport, La., in 1960 that became even poorer after his father walked out and left his mother to raise six children alone. “After he left, we couldn’t afford to live in the projects anymore,” he once told an interviewer.

Mr. Cochran aspired to be a firefighter from age 5, and he eventually was appointed Shreveport’s first black fire chief in 1999. In 2008 he became the fire chief of Atlanta. And In 2009 President Obama appointed him U.S. fire administrator, the top position in the profession.

At the urging of Democratic Mayor Kasim Reed, Mr. Cochran returned to his post in Atlanta in 2010 and continued to impress. In 2012, after more than 30 years of service, he was given a Fire Chief of the Year Award by Fire Chief magazine. In a related press release, the mayor’s office said that “under Chief Cochran’s leadership, the department has seen dramatic improvements in response times and staffing.” Mr. Reed added: “Chief Cochran’s pioneering efforts to improve performance and service within the Atlanta Fire Rescue Department have won him much-deserved national recognition.”

But a year ago, Mr. Cochran was suspended for 30 days without pay, pending an investigation into his behavior. On Jan. 6, at the end of the suspension, Mr. Reed sacked him. Mr. Cochran’s fireable offense, according to the city, was publishing a book in violation of the city’s ethics code and without permission from the mayor. The reality, according to a lawsuit filed in response to the firing, is that Mr. Cochran no longer has his $172,000-a-year job because of what’s in the book. The suit accuses the city of firing Mr. Cochran for his religious beliefs.

It turns out that when he’s not fighting fires, Mr. Cochran spends a lot of time helping black men turn their lives around and stay out of trouble. He does this under the auspices of Atlanta’s Elizabeth Baptist Church, where he is a deacon and leads a men’s bible study.

Mr. Cochran self-published a book in 2013, “Who Told You That You Were Naked?” The book, written on his own time, is a compilation of lesson plans for his bible classes and explains how the teachings of Christ can help men fulfill their purpose as responsible husbands and fathers. What earned the ire of Atlanta officials is that the 162-page tome includes a few passages criticizing homosexual conduct as “perversion.”

In response to the lawsuit, the city has maintained that Mr. Cochran was terminated for violating protocol, not for his religious views—as if he would have been fired for publishing a cookbook. But comments from the mayor and other city officials at the time of the suspension suggest that the book’s content is what drove the decision.

“I want to be clear that the material in Chief Cochran’s book is not representative of my personal beliefs, and is inconsistent with the administration’s work to make Atlanta a more welcoming city for all of her citizens—regardless of their sexual orientation, gender, race and religious beliefs,” said Mr. Reed. Alex Wan, a member of the City Council who is openly gay, said “I respect each individual’s right to have their own thoughts, beliefs and opinions, but when you’re a city employee, and those thoughts, beliefs and opinions are different from the city’s, you have to check them at the door.”

So the mayor fired someone who disagreed with him in the name of inclusivity and tolerance. And Mr. Wan believes that government employees are entitled to their own views but not entitled to share them with anyone. If this is true, the Constitution’s protections of free speech and freedom of religion are meaningless in practice.

David Cortman of Alliance Defending Freedom, the legal group representing Mr. Cochran, says the city is now using protocol arguments to cover its tracks after wrongly terminating someone for holding and expressing religious views that city officials didn’t like. There is no official requirement to notify the mayor before you write a book, Mr. Cortman told me, and Mr. Cochran sought and received permission from the city’s ethics department to pursue the book project.

“The ethics rule concerns moonlighting, other employment or outside work,” said Mr. Cortman. “It doesn’t apply to writing a book, religious or otherwise, on your own time at home. And if they had such a rule in place it would be unconstitutional. You don’t need the government’s permission to do that.”

Despite the left’s efforts to paint Mr. Cochran as some kind of hateful bigot, the city’s own investigation of the former fire chief’s work history found no complaints of discrimination.

Many Americans—and polls show their numbers growing—don’t agree with Mr. Cochran about sexual behavior or same-sex marriage, but all Americans have a stake in religious freedom. Consider: Would it be OK for a mayor who holds traditional views on marriage to fire an employee who wrote a book that expressed support for same-sex marriage?

“Our nation was founded on the principle that everyone should be free to not just believe what they want, but to live their lives according to those beliefs,” said Mr. Cochran in a statement last month following a court hearing. “I’m here today not just for myself, but for every religious person in America who does not want to live in fear of facing termination for expressing their faith.”

Mr. Riley, a Manhattan Institute senior fellow and Journal contributor, is the author of “Please Stop Helping Us: How Liberals Make It Harder for Blacks to Succeed” (Encounter Books, 2014).