In the Liberty you provided answers to those who hate free speech. Your main explanation was bracingly utilitarian, as befitted the son of James Mill. We value free speech, you wrote, because human beings are fallible and forgetful. Our ideas must be tested by argument: wrong opinion must be exposed and truth forced to defend itself, lest it “be held as a dead dogma, not a living truth.” (Your consequentialist followers said a flourishing marketplace of ideas was a precondition of participatory democracy and even of an innovative economy.)
Jason Pontin writes a letter to John Stuart Mill on the current challenges of free speech in the context of Google, Facebook and Twitter.