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...there ought to exist the fullest liberty of professing and discussing, as a matter of ethical conviction, any doctrine, however immoral it may be considered.

John Stuart Mill (2008). “Utilitarianism and On Liberty: Including 'Essay on Bentham' and Selections from the Writings of Jeremy Bentham and John Austin”, p.99, John Wiley & Sons
...there ought to exist the fullest liberty of professing and discussing, as a matter of ethical conviction, any doctrine, however immoral it may be considered.