After Elliot Rodger went on a rampage Friday, killing six people and himself, fan pages glorifying the 22-year-old Californian sprung up on Facebook.
The social networking site has removed the pages, some as early as Sunday morning. But even as Facebook took down controversial pages, new ones popped up, illustrating the challenges websites face in monitoring hate speech.
Although sites such as Facebook and YouTube try to create a community with civil, respectful discourse, they are "often outpaced" by the amount of content constantly posted, said Danielle Citron, a professor at the University of Maryland's School of Law and author of the book Hate Crimes in Cyberspace, in an interview with USA TODAY Network.
The Facebook fan pages, including one titled "Elliot Rodger is an American hero," praise the killer. Facebook had taken down the "American hero" fan page, but another version of the page emerged Tuesday, which was taken down hours later.
Facebook and YouTube both set forth community guidelines and allow users to report abuse. Facebook has hundreds of reviewers worldwide who follow up on these reports around the clock, according to the social network's website.
On YouTube, Rodger's account has been stripped of his controversial homemade videos. Forbes reported his family had taken down those videos. But other YouTube users reposted them. A search "Elliot Rodger retribution" returns thousands of results.
YouTube said content posted in a "news context" will be allowed to stay online, a company spokesperson told Mashable.
Although Facebook and YouTube, as private companies, can ban hate speech, any threatening or offensive speech against a particular group of people is allowed under the law.
The only speech that's not protected under the law is "a very small pocket" that includes threats against a specific person or incitement of imminent violence, Citron said.
Where they can, individual users can report hate speech to the website where it appears. Online users can also speak out against such speech, engaging in what Citron refers to as counter-speech.
"We're not off the hook as online users," she said. "We're all digital citizens."
In response to Rodger's comments about women, tweeters used the hashtag #YesAllWomen to share stories of harassment, violence and fear.
Citron acknowledged that the backlash against counter-speech can be even worse than the initial comments, and some tweeters make their comments anonymously.