[inquest]

It could be that Mill justified an empire if it was benevolent and well meaning (the British Empire, e.g.), if it brought classical liberalism to the backward civilizations of the world.

That's odd. I could see condemning that if it were a liberal's list of harmful books. But for conservative scholars to react that way? Tough for me to visualize. (I'm not saying you're wrong, though)

[WOSG]

Mill jumped on to Benthamite "utilitarianism", did he not?

Utilitarianism is an incorrect and dnagerous moral stance that has been a basis for 'collectivism' ethics in the 20th century. It could be for that reason that it was deemed harmful.