“Insulting the Prophet is something that has been going on in Europe for a very long time. In Dante's Inferno, if you're interested in the 28th Canto, where Dante is being taken on his conducted tour of hell and guided by Virgil, he comes across the Prophet Mohammed in the course of his eternal damnation. He is punished I quote Dante's words, as a seminator di scandalo e di scisma, a sower of scandal and of schism. Now, this is very insulting. In the great Cathedral of Bologna there is a wonderful set of pictures painted, if I remember rightly, in the 15th century depicting scenes from Dante's Inferno, including some very graphic pictures of Mohammed being tortured in hell by the devil very graphic.
Nobody did anything about this. A couple of years ago, the leaders of the Italian-Muslim community sent a polite request to the cathedral saying these are insulting to Muslims; would they mind covering those pictures. The cathedral administration said they would consider it. Nothing happened. The pictures are still in view.”

Napoleon : In His Own Words (1916)
Context: Dante has not deigned to take his inspiration from any other. He has wished to be himself, himself alone; in a word, to create. He has occupied a vast space, and has filled it with the superiority of a sublime mind. He is diverse, strong, and gracious. He has imagination, warmth, and enthusiasm. He makes his reader tremble, shed tears, feel the thrill of honor in a way that is the height of art. Severe and menacing, he has terrible imprecations for crime, scourgings for vice, sorrow for misfortune. As a citizen, affected by the laws of the republic, he thunders against its oppressors, but he is always ready to excuse his native city, Florence is ever to him his sweet, beloved country, dear to his heart. I am envious for my dear France, that she has never produced a rival to Dante; that this Colossus has not had his equal among us. No, there is no reputation which can be compared to his.

Source: When Darkness Comes

The Tragic Sense of Life (1913), Conclusion : Don Quixote in the Contemporary European Tragi-Comedy

1840s, Heroes and Hero-Worship (1840), The Hero as Poet

2000s, Burning embassies is not the way (2008)

The Satanic Bible (1969)

Ernest Renan, at the dedication of a statue to Spinoza in 1882, as quoted in The Story of Philosophy (1962) http://caute.net.ru/spinoza/aln/durant.htm by Will Durant
Context: Woe to him who in passing should hurl an insult at this gentle and pensive head. He would be punished, as all vulgar souls are punished, by his very vulgarity, and by his incapacity to conceive what is divine. This man, from his granite pedestal, will point out to all men the way of blessedness which he found; and ages hence, the cultivated traveler, passing by this spot, will say in his heart, "The truest vision ever had of God came, perhaps, here."

King quoted here John F. Kennedy who at the signing of a charter establishing the German Peace Corps in Bonn, West Germany (24 June 1963) remarked: Dante once said that the hottest places in hell are reserved for those who, in a period of moral crisis, maintain their neutrality.
According to Bartleby.com, Kennedy's remark may have been inspired by the passage from Dante Alighieri’s La Comedia Divina “Inferno,” canto 3, lines 35–42 (1972) passage as translated by Geoffrey L. Bickersteth: "by those disbodied wretches who were loth when living, to be either blamed or praised. [...] Fear to lose beauty caused the heavens to expel these caitiffs; nor, lest to the damned they theng ave cause to boast, receives them the deep hell." A more modern-sounding translation from the foregoing Dante’s Inferno passage was translataed 1971 by Mark Musa thus: “They are mixed with that repulsive choir of angels … undecided in neutrality. Heaven, to keep its beauty, cast them out, but even Hell itself would not receive them for fear the wicked there might glory over them.”
This is also often quoted slightly differently as: "The hottest place in Hell is reserved for those who remain neutral in times of great moral conflict"
1960s, Why I Am Opposed to the War in Vietnam (1967)
Context: I see this war as an unjust, evil, and futile war. I preach to you today on the war in Vietnam because my conscience leaves me with no other choice. The time has come for America to hear the truth about this tragic war. In international conflicts, the truth is hard to come by because most nations are deceived about themselves. Rationalizations and the incessant search for scapegoats are the psychological cataracts that blind us to our sins. But the day has passed for superficial patriotism. He who lives with untruth lives in spiritual slavery. Freedom is still the bonus we receive for knowing the truth. "Ye shall know the truth," says Jesus, "and the truth shall set you free." Now, I've chosen to preach about the war in Vietnam because I agree with Dante, that the hottest places in hell are reserved for those who in a period of moral crisis maintain their neutrality. There comes a time when silence becomes betrayal.