Voltaire: “He who can make you believe absurdities can make you commit atrocities.”
Me: Yeah, just look at what happened with ‘Liberty, Equality, Fraternity.’
Of course, what you consider an atrocity is largely dependent on what you believe to be an absurdity, so that the statement, upon examination, only means “thinking the wrong thing means you’ll do the wrong thing.”
Which is true, but can’t of itself be made to tell against any specific philosophy apart from pluralism.
Which seems to be what it’s usually cited in favor of.