John Stuart Mill backs the prosecution of people who incite violence on Twitter shock

I've been known to complain that the only time you hear John Stuart Mill's On Liberty quoted is when someone is citing Mill's Harm Principle. And when they are, you can be sure they are using it to justify state intervention.

You rarely get reminded by today's Liberal Democrats that On Liberty is a hymn to individuality and its importance to our wellbeing.

But Mill lived in an age more used to political violence than we have become, so it's worth studying what he has to say on incitement:

No one pretends that actions should be as free as opinions. On the contrary, even opinions lose their immunity, when the circumstances in which they are expressed are such as to constitute their expression a positive instigation to some mischievous act. 

An opinion that corn-dealers are starvers of the poor, or that private property is robbery, ought to be unmolested when simply circulated through the press, but may justly incur punishment when delivered orally to an excited mob assembled before the house of a corn-dealer, or when handed about among the same mob in the form of a placard.

Or when broadcast on social media in a way likely to move people to violence, as I'm sure Mill adds somewhere.