Those who do not learn from history are doomed to repeat it. Even when presented with proof that one idea is more effective than another, the same arguments arise again. This is deeply problematic in the context of society. If all opinions can be shared at any time, there is nothing to stop the emergence of a new slavery lobby, the legalization of human trafficking, or other insidious practices that have been rightly criminalised. Censorship of ideas that society has collectively condemned, is necessary for social progress.
Western progress in civil rights, economic principles, and liberty show that when opinions are given air to be debated, the truth almost always prevails and humanity moves forward. Sound arguments and truth languish without alternatives by which they can be compared. Giving government the power to outlaw ideas deemed subjectively wrong threatens free speech. John Stuart Mill supported the notion of continually giving wrong opinions a stage so that the public might gain a “clearer perception and livelier interpretation of truth”.