Yeah CA is kind of a wildcard.
To begin with, conservative America (which is a vocal minority) absolutely hates California because it is a bastion of liberal thought. You have Berkeley, San Fransisco, etc etc. Not surprisingly, California is also where many originally "intelligentsia" concepts got started, for example the Internet and computing itself exists as it does today in large part thanks to various schools, organizations, and businesses in California.
So you have that part of the CA-hate. There's also the fact that California is seen as the bastion of "the liberal media", largely due to Hollywood -- if you don't know a lot about U.S. histroy, there was a period during the cold war when many people in Hollywood were blacklisted and called out for being communist. Look up "McCarthyism". That general feeling amongst the right-wing that Hollywood (also variously representing media in general) harbors "America-haters" still exists.
There are also people who CA-hate for non-political reasons. Californians are ascribed various attributes: fake, snobbish, too happy, ignorant, detached from reality, etc. The general idea is that Californians don't really represent "real people" or the "average American", and thus because California is unrepresentative it should "fall into the ocean" or whatever.
People that like California generally share two traits: a)They've actually been there; and b)They aren't miserable, jaded people. They like California because it's always 72 degrees and partly cloudy, there's enough beach for everyone and when you're sick of that you can drive a couple of hours and be in the mountains, you can get to know our friendly, hardworking neighbors to the south, the climate is perfect for preserving classic automobiles, and so on.
There are other CA-haters who are just jealous of the above.
Nad then there's the who nor-Cal vs. so-Cal thing. That's an entirely different issue.
In many ways, California is entirely different than the rest of the U.S. In other ways, it perfectly resembles a microcosm of the U.S. It may actually be this dichotomy that's at the true heart of CA-hate.