Facebook's advertising tools failed to protect the civil rights of its users. The company is allowing advertisers to exclude users based on their racial background.

According to ProPublica's recent investigation, Facebook not only allows advertisers to target users, but it also gives them the ability to exclude specific groups that it calls "Ethnic Affinities." The exclusion of people in advertisements based on race, gender, and other sensitive factors are prohibited by the federal law in housing and employment.

The publication said they tried to purchase a targeted ad in the housing category and saw that Facebook allowed them to exclude "Ethnic Affinities," which include African-American, Asian-American and Hispanic people. They showed the ad to John Relman, a civil rights lawyer, and he said it is "massively illegal."

"This is horrifying," Relman said. "This is about as blatant a violation of the federal Fair Housing Act as one can find."

The Atlantic asked Rachel Goodman, a lawyer at the American Civil Liberties Union, about this and she said Facebook should at least prohibit the targeting of ads in housing, credit or employment. She said that targeting ads based on gender, race, or sexual orientation in these three categories violate federal civil-rights laws that cover those fields.

A spokesperson for Facebook said that ProPublica's ad was not promoting a rental property. The ad was promoting an event about the rights of renters.

Facebook's Privacy and Public Policy Manager Steve Satterfield told ProPublica that they have "a strong stand against advertisers misusing their platform." He said it is in their policies to prohibit the use of their targeting option to discriminate, and they require that targeted ads should comply with the law.

Satterfield adds that the "Ethnic Affinity" is not the same as race, as Facebook assigns members an "Ethnic Affinity" based on pages and posts the member have liked or engaged with. The "Ethnic Affinity" option has been around for two years.