If Alan Ryan wants universities to "nourish the dissenter...", he should go not to John Stuart Mill, but to the critical hermeneutics and ecologism explaining closed minds and the causes of our woes.
The doctrine of externalism Mill shares with analytic philosophy splits practice and thought, is and ought, causes and justification, since it sees their relation as contingent and necessary, not internal.
To make Mill a hero of free speech and anti-racism splits his public life and theory. Defining freedom and harm calls for an epistemology and ethics that he does not have.
David Rodway
Woldingham, Surrey