Facebook is probably the worst offender. It consistently allows racist content on it's site and ignores complaints.
"Major European clients are pulling their ad dollars out of Google and YouTube because of fears that their ads will end up next to videos promoting terrorism, racism and hate, and earn money for the extremists who posted the content.
Three of Britain’s biggest banks just removed their ads from Google when they saw their campaigns appearing next to extremist content.
According to Adweek and the Guardian, ad agency giant Havas Worldwide has also yanked all its ad money out of Google and YouTube in Britain, after Havas and Google couldn’t agree on how to keep the ads of French firm’s clients away from videos of terrorists and white supremacists.
McDonald’s, Audi, and the U.K. government have already stopped using the platforms in the U.K., amid concerns that extremist groups will earn money from their advertising. When an ad appears alongside a YouTube video, the individual or organization that posted video earns a small amount of money per viewing of the video."
Companies Pull Ads From Google, YouTube Over Racist, Terrorist Content - NBC News