I also know many people like that, unfortunately too many in my own family. They never have any good reason for their hatred, but after long observation of them, and by living quite a few years in many of the Left's bastions (Boston, NY, DC, SF), I have a general theory.
It is intellectual pageantry. They are overimpressed with their own intellects, and feel that nobody exuding a folksy commonsense 1950's sense of decency can possibly have a clue as to the nuanced sophistication of modern-day knowledge and current societal paradigms. They are "progressives", in their own minds, because they have moved on from the simplistic world view held by dinosaur Republicans living in "Leave It To Beaver" Land.
Every time I hear a liberal caller to a conservative talk show, I hear the exuberant smugness of intellectual superiority in their voices. Never mind that they uniformly get dissected and splayed out for all listeners, they go back to their liberal friends - and mischaracterize the "battle" as stumping the host.
My general response to them is that they are too smart by half, and that they are only part-way around the circle of wisdom. They hate to hear things like "The more things change, the more they remain the same." And they are completely flummoxed by people like P.J. O'Rourke - who was a Leftist long enough to see the general idiocy of their philosophy - and now can eviscerate liberals with a single sideswipe of his pen.
I think they all should be looked straight in the eye and told "You don't impress with your fashionable intellectual elitism, because it is absolutely no substitute for wisdom, nor a solid grasp of logic, facts and history."