But just now I read an essay by Thomas Sowell which explains it. I reproduce the key passage:
"What socialism, fascism and other ideologies of the left have in common is an assumption that some very wise people -- like themselves -- need to take decisions out of the hands of lesser people, like the rest of us, and impose those decisions by government fiat.
The left's vision is not only a vision of the world, but also a vision of themselves, as superior beings pursuing superior ends. In the United States, however, this vision conflicts with a Constitution that begins, "We the People..."
That is why the left has for more than a century been trying to get the Constitution's limitations on government loosened or evaded by judges' new interpretations, based on notions of "a living Constitution" that will take decisions out of the hands of "We the People," and transfer those decisions to our betters.
The self-flattery of the vision of the left also gives its true believers a huge ego stake in that vision, which means that mere facts are unlikely to make them reconsider, regardless of what evidence piles up against the vision of the left, and regardless of its disastrous consequences." (emphasis mine)
Thank you, Dr. Sowell! This makes sense. It explains the intellectual snobbery of those on the left, their obvious attitude that anyone who disagrees with them just can't be too bright, that their opponents are lesser beings--perhaps even subhuman!--and needn't be treated with the respect one would extend to a fellow human being.
"And the serpent said to the woman, "You will not surely die. For God knows that in the day you eat of it your eyes will be opened and you will be like God, knowing good and evil." (Gen. 3:4,5)