https://www.theverge.com/2017/9/22/16347338/facebook-google-hateful-ad-targeting-by-design

Facebook and Google, two of world’s biggest and most influential companies, pride themselves on their ad businesses. These operations generate tens of billions of dollars per year, thanks in part to letting advertisers target even the most obscure microcommunities using unprecedented sets of data. As the revelations of last week evidenced, however, that ability is a double-edged sword, one that has come back to haunt these ad-supported giants.

ProPublica discovered last Thursday that Facebook’s ad tools could target racists and anti-Semites using the very information those users self-report. That initial report kicked off a series of experiments conducted by news organizations that found that Google’s search engine would not only let you place ads next to search results for hateful rhetoric, but its automated processes would even suggest similar, equally hateful search terms to sell ads against. Twitter was also caught up in the controversy, when its filtering mechanisms failed to prevent ads from targeting “Nazi” and the n-word, an issue the company inexplicably attributed to “a bug we have now fixed.” This week, Instagram converted a journalist’s post about a violent threat she received into an ad that it then served to the journalist’s contacts.