“If at first the idea is not absurd, then there is no hope for it.”

2010s, 2016, Democratic Presidential Debate in Miami (9 March 2016)
Context: Poverty is increasing. And if wages are going down, I don’t know why we need millions of people to be coming into this country as guestworkers who will work for lower wages than American workers and drive wages down even lower than they are right now.... You have guestworker programs that have been described by the.... In this country, immigration reform is a very hot debate. It’s divided the country. But I would hope very much, that as we have that debate, we do not, as Donald Trump and others have done, resort to racism and xenophobia and bigotry. This idea of suddenly, one day or maybe a night, rounding up 11 million people and taking them outside of this country is a vulgar, absurd idea that I would hope very few people in America support.

The Myth of Sisyphus (1942), An Absurd Reasoning

Possibly a paraphrase of Bertrand Russell in My Philosophical Development (1959): "This is one of those views which are so absurd that only very learned men could possibly adopt them." It is similar in meaning to Orwell's line from Notes on Nationalism (1945): "One has to belong to the intelligentsia to believe things like that: no ordinary man could be such a fool." However, Russell was commenting not on politics, as Orwell was, but on some philosophers and their ideas about language.
Misattributed
Variant: Some ideas are so stupid that only intellectuals believe them.

Source: Modern thinkers and present problems, (1923), p. 217-18; : Partly cited in: John Barton, " Pragmatism, systems thinking and system dynamics http://courses.daiict.ac.in/pluginfile.php/19296/mod_resource/content/1/Pragmatism%20and%20systems%20Thinking.pdf." 19th International System Dynamics Conference, Wellington, New Zealand. AusAID, 1999.
Context: Looking back over the years that have lapsed since this was written, I cannot say that James's prophecy as to the future of pragmatism has been fulfilled; but that the world, at least the world in which I have lived, has lost its first sense of the absurdity of pragmatism is undoubtedly true. No one was more bitten than I with this first feeling of the absurd, unless it was some other of my kind among those who gathered of an evening in 1896 to listen to a reading of James s now famous little essay on " The Will to Believe " the essay which, so far as James was concerned, opened the campaign for pragmatism. James had written the paper that winter as a lecture to be delivered before the Philosophical Clubs of Yale and Brown Universities, and I cannot recall what the occasion was that brought a small number of us graduate students at Harvard together to hear it re-read but I do recall that we were very much bewildered and not a little shocked by the reading.

The First Part, Chapter 5, p. 20 (See also: Algorithms).
Leviathan (1651)
Context: The first cause of Absurd conclusions I ascribe to the want of Method; in that they begin not their Ratiocination from Definitions; that is, from settled significations of their words: as if they could cast account, without knowing the value of the numerall words, one, two, and three.

Source: QED: The Strange Theory of Light and Matter (1985), p. 10

Quoted in Amnesty International's essay "From Prisoner to President – A Tribute"