Facebook said it was revising its advertising policies to prevent "discriminatory" targeting after a news report showed marketers could aim messages at categories of people such as "Jew haters."

The world's biggest social network announced the change after the non-profit investigative news site Pro Publica on Thursday revealed how advertisers could target messages to demographic categories including anti-Semitic segments.
Facebook product manager Rob Leathern said Friday that the company had changed its ad targeting policy after learning about the report, saying these messages represented "hate speech" prohibited by Facebook.
"Our community standards strictly prohibit attacking people based on their protected characteristics, including religion, and we prohibit advertisers from discriminating against people based on religion and other attributes," Leathern said in a statement to AFP.
"However, there are times where content is surfaced on our platform that violates our standards. In this case, we've removed the associated targeting fields in question. We know we have more work to do, so we're also building new guardrails in our product and review processes to prevent other issues like this from happening in the future."
The Pro Publica team said that, acting "on a tip," it had logged into Facebook's automated ad system and discovered "Jew hater" as an ad category, with 2,274 people in it (they had expressed interest in topics like "How to burn Jews" and "History of 'why Jews ruin the world'").
Because targeted ads are not sold for such small groups, the automated system suggested the category "Second Amendment" -- the right under the US Constitution to bear arms -- as an additional category. Its system had correlated gun enthusiasts with anti-Semites.
The report said the anti-Semitic categories were created by algorithm rather than by people, based on information Facebook users supply in their profiles and other data.
A Facebook statement said the company had found "a small percentage of people who have entered offensive responses" in their profiles and "immediately removed them."
"To help ensure that targeting is not used for discriminatory purposes, we are removing these self-reported targeting fields until we have the right processes in place to help prevent this issue," the company said.