Twitter CEO Jack Dorsey said he would give himself a “C” when it comes to grading his company's protection of victims of online abuse, Reuters reports. The media mogul wrote in a Twitter interview Tuesday that his company and others in Silicon Valley have not done enough to protect social media users. “We’ve made progress, but it has been scattered and not felt enough,” he tweeted in response to questions from Kara Swisher, co-founder of the tech news site Recode. “Changing the experience hasn’t been meaningful enough. And we’ve put most of the burden on the victims of abuse (that’s a huge fail).” Dorsey added that he doesn't like how Twitter tends to encourage outrage, short-term thinking, echo chambers and fragmented conversations, and that the lack of diversity in the company has not helped in combating such problems. Social media sites including Twitter and Facebook have faced criticism for abusive posts, fake user accounts, and inaccurate news stories disseminated through the platforms. Twitter has reportedly invested heavily to improve what Dorsey has described as the “collective health” of the platform.