Unfortunately, "Black Twitter" is far from violent. It's a community of people on the Internet who talk about things related to race, as BuzzFeed's Shani O. Hilton explains it:
Black Twitter is, loosely speaking, a group of thousands of black Twitterers (though, to be accurate, not everyone within Black Twitter is black, and not every black person on Twitter is in Black Twitter) who a) are interested in issues of race in the news and pop culture and b) tweet A LOT.
Black Twitter had been talking about the Trayvon Martin case since the trial began. "The constant hum grew as everyday people turned to the livestream and tweeted what they saw," Hilton explains. The focus turned to Juror B37 when news came out about the book deal, after one black tweeter started a change.org petition:
After murdering Trayvon Martin, George Zimmerman was acquitted, even though juror B37 admitted (in a CNN interview) that Zimmerman "went too far", and didn't "stop at the limitations he should've stopped at". Now that very juror, who allowed Trayvon Martin's killer to get away, is writing a book. Please don't allow this person to profit off of the injustice that they've served to the American public. We deserve better. Trayvon Martin's family deserves better.
Then, the word spread on Black Twitter, and, a Drudge asserts, these people successfully bullied the Juror into backing down from the book deal.
It's the perfect symbol of unreasonable retribution that conservatives had hoped would happen in the form of pillaging—but only if you disregard what Twitter is and how everyone else on the site uses it. "Black Twitter’s power makes perfect sense—as long as you don’t consider black Twitterers to be some mysterious 'other' group," notes Hilton. Any group of people on Twitter can make a hashtag and tweet about it. The "Twitter mob" isn't limited to angry black people. Occupy Wall Street, feminists, Anonymous—they've all aggressively angry-tweeted things until they got their way.
That tactic isn't very violent, either. If anything, it's the Internet version of a peaceful protest—so much so that, Essence's Jeannine Amber insists Martin Luther King Jr. himself would use it. "If Dr. King was alive today, of course he would use Twitter because that's how everyone is getting out the messages to the most number of people most effectively and you know you have the farthest reach," she told CNN.