“If liberty means anything at all, it means the right to tell people what they do not want to hear.”
George Orwell book Animal Farm
Sometimes paraphrased as "Liberty is telling people what they do not want to hear."
Variant: Freedom is the right to tell people what they do not want to hear.
Source: Original preface to Animal Farm; as published in George Orwell: Some Materials for a Bibliography (1953) by Ian R. Willison