Precisely. It's all built on fear of the *other*, as long as that other is not a conservative straight white male.

You got the 'why' right. The 'how' was the rise of right-wing media that told their viewers and listeners, "Only listen to us. Only we tell you the truth. It is an actual sin before God to listen to - much less work with - a liberal."

And that's why, no matter how good and right and beneficial the Dems' policies are (even if they were originally Republican ideas like the Affordable Care Act), the Right feels they are bound by God and honor to oppose it.