The Red & Black Cafe is no place for a man in blue.

Police Officer James Crooker was asked to leave the vegan coffee shop in Portland, Ore., last month, a discriminatory move but not altogether uncommon at the java joint, a detective told FoxNews.com.

Crooker, 36, a 2-year veteran of the force, entered the Red & Black Café on May 18 and bought a cup of coffee before a customer approached him and said she appreciated his efforts.

That's when John Langley, one of the co-owners of the collectively managed shop, approached the cop and asked him to leave.

Crooker left immediately. It was the first time something like this has happened to him in his nine-year law enforcement career, he told The Oregonian newspaper.

"The places that I've been kicked out of before have been places like the methadone clinic," he said. "You're there to protect them, but on the other hand they don't know what that involves. Being gracious is part of it."

Detective Mary Wheat, a spokeswoman for the Portland Police Department, characterized the incident as a "fluke" but noted the city's ongoing tension between the police and some members of the community.

"This is Portland," Wheat told FoxNews.com. "We have been dealing with that for years and years and years. It's a very liberal city. We have anarchists here and we deal with them on a regular basis."

The coffee shop attracts homeless individuals and activists, the newspaper reported, and Wheat said it is known to be "not friendly" to officers who work the area.

"Most officers would know that this is not a coffee shop that's friendly to police," she said. "It's obviously discrimination to police. He works that area and he can't go in for a cup of coffee -- it's not fair."

The customer who approached Crooker, Cornelia Seigneur, is a freelancer for The Oregonian who blogged about the incident on her website.

"As I spoke with the café owner, I really never got a direct answer as to why he personally felt unsafe with a police officer in his establishment," Seigneur wrote. "Bottom line, I think especially of the policeman I met at the red and black, Officer James Crooker, a human being who should be treated with respect and honor, like all human beings."

Neither Crooker nor Langley could be reached for comment on Friday. An employee who answered the phone at the Red and Black café declined to discuss the incident.

"I've been taking calls about this all day and I'm kind of tired of talking about it," the employee said. "I have a regular job."