It started relatively early in the blogging days, soon after Bush was elected for the first time, and blogs were fewer, further between, and only sometimes actually called blogs.
There was a blog I was following by a guy named 8Ball, which I'll use for illustrative purposes; it demonstrates things I was seeing more broadly. Anyway, his posts were infrequent, but frequently hilarious; he figured out the size necessary for Noah's ark, for example, and calculated that the great flood actually happened, and happened because Noah shoved this giant-ass boat into a sea and the displacement caused said massive flood.
His version was more hilarious, involving the extinction of gopherwood trees and other such things. I'd link it but I can't find the blog anymore; it has likely been taken down in the intervening years.
In those days, I still leaned liberal; I wasn't a hardcore liberal, I just shared many of their views, including the idea that, to put it bluntly, conservatives were fanatical Christians and/or poor white trash. The world needed saving from their brutish, outdated ideals, based in religious fervor rather than reason.
Now, 8Ball was, in an interesting twist, both black and stereotypically liberal, which included (although I doubt he, like most liberals, would ever actually admit to this) a deep-set racism against black people, which he apparently felt, being black, wasn't really racism. This made the reading more entertaining, both also more uncomfortable, particularly when he started talking about Africa, a subject with which he had some obsession. (He went on about some length about witch hunts and the like.)
The racism, combined with a curious kind of contempt I've later come to understand is "cultural relativism" (which in liberal circles is a way of saying "They just don't know any better" without saying who "they" are), put me off, and I started to regard the liberals with some skepticism; too much of their "good will," too much of "doing good for others" was wrapped up in a contempt I didn't recognize until years later - reading the justifications of slavery and imperialism, that the natives/black people just didn't know any better, and were better off under the rule of more civilized people who would take care of them.
So the blog was off-again uncomfortable, on-again hilarious. Up until a few months after 9/11, when he, along with most of the liberals I had until then respected, went absolutely batshit insane.
Now the conservatives also went insane, but it was a different kind of insane; they decided we were now At War, and many aspects of morality suddenly became optional, and the flying of flags suddenly became mandatory. I had contempt for them - and still do, such reactionary patriotism is not patriotism at all but fear, and I have little use for patriotism to begin with.
So the conservatives went insane. But the liberals - there was a variety of kinds of insane there, but it was also neurotic; they weren't fearful people reacting to a tragedy, they nearly universally turned to the kind of vitriolic hatred that they so desperately want to accuse conservatives of. You had atheists like Richard Dawkins and Bill Maher who went flat-out fuckin' antitheist. You had socialists who suddenly decided we were doomed to fascism under a Bush Regime, and were constantly looking for proof of a grand conspiracy to seize power in this country. You had communists who decided capitalism was to blame and America deserved what it had gotten.
And everybody I had been patiently following until then, including 8Ball, were all of a sudden total fucking lunatics.
And as time went on things got -worse-, not better. I was disillusioned by the people who claimed so loudly to be scientific and rational, helped along by no small degree by a significant number among them supporting global warming nonsense which just plain smelled wrong to me. Now I seriously -believed- in science - I still do. And what they called science wasn't.
And I just stopped believing in them. Not then, and not since then, have I seen anything to suggest to me that liberalism is not in fact founded on contempt. Whether the green contempt of humans as humans, or the communist's contempt of human beings as rational creatures, or the socialist's contempt of people's ability to run their own lives, the uniting factor of the modern liberal is a deep-set contempt.
It came unmasked after 9/11. And I've seen it unmasked on more than one occasion since then; liberals outright admitting to their contempt for their fellow human beings, whether by declaring that the only way charity can function is by taking it by force from others, others who cannot be relied upon to behave the way the liberal wants, or by declaring that a policeman's gun is the only thing keeping people from robbing everybody else, or a thousand other minor contempts.
Modern liberalism -is- contempt.