W.e.b. Du Bois said this quote

The hushing of the criticism of honest opponents is a dangerous thing. It leads some of the best of the critics to unfortunate silence and paralysis of effort, and others to burst into speech so passionately and intemperately as to lose listeners. Honest and earnest criticism from those whose interests are most nearly touched,—criticism of writers by readers, of government by those governed, of leaders by those led,—this is the soul of democracy and the safeguard of modern society.