Facebook isn't shy about policing the site for material it deems inappropriate. "Graphic content for sadistic pleasure" is strictly prohibited, as is hate speech directed at specific targets. Per the social network's Community Standards (emphasis added):

Facebook does not permit hate speech, but distinguishes between serious and humorous speech. While we encourage you to challenge ideas, institutions, events, and practices, we do not permit individuals or groups to attack others based on their race, ethnicity, national origin, religion, sex, gender, sexual orientation, disability or medical condition. [Facebook]

Which is why thousands are up in arms over Facebook's recent hand-wringing over graphic images and depictions that glorify rape and physical violence towards women. Critics call it "rape culture," and argue that the implicit message categorically qualifies as hate speech — but Facebook has been reluctant to take the images down. (Warning: Some of the following photos are pretty graphic. And these are relatively tame compared to others.):

Here's one Facebook response to a takedown request:

In response, Twitter and Tumblr users have been uniting under the #FBrape banner, and are calling on Facebook to remove the offending photos. The movement is led by a group called Women, Action, & the Media, which aims to end "gender-based hate speech on Facebook."

To date, activists have sent more than 4,000 emails to Facebook advertisers to remove their ads (which can appear next to offensive content), and have posted more than 60,000 messages on Twitter. According to Bloomberg Businessweek, the shortlist of advertisers includes Zappos, Zipcar, and Dove. Nissan and Nationwide Bank, meanwhile, have halted some of their ads.

Here's one example of how an ad can appear in the right-hand module, via BuzzFeed:

Facebook, to its credit, responded today in a blog post that "it has become clear that our systems to identify and remove hate speech have failed to work as effectively as we would like, particularly around issues of gender-based hate." The social network is promising to improve its standards.

In some cases, content is not being removed as quickly as we want. In other cases, content that should be removed has not been or has been evaluated using outdated criteria. We have been working over the past several months to improve our systems to respond to reports of violations, but the guidelines used by these systems have failed to capture all the content that violates our standards. We need to do better — and we will. [Facebook]

To be clear: Hate speech, while deplorable, still falls under First Amendment protections. On the other hand, Facebook is entitled as a business to police itself however it deems fit. The issues at hand are nothing new, and as technology, the Internet, and social media continue to evolve, we'll surely run into them again.