People point to different inflection points and a multitude of influences and no doubt they all have merit, but growing up in the 60s and 70s there was a visceral loathing of people viewed as liberal. Think of "All in the Family" - Mike and Gloria, and how Archie loathed everything Mike stood for. I mean a visceral loathing though Carroll O'Connor pulled it off with humor. My family thought that show was a how-to show, never realizing the sarcasm embedded.
The irony, which many of us have pointed out repeatedly, is that the qualities they seem to loathe truly are the qualities most people associate with Jesus, and most of the right-wingers consider themselves Christian.
But the whole "tree-huggin' liberal peace freak" hatred has been around since my childhood, and I do wonder if the extreme societal divide started then, with the anti-war movement associated with hippies and the now larger-than-life stories of soldiers being spat upon when they returned from war. Of course we know the political class has manipulated cultural issues forever and the anti-war, pro-environment, pro-choice side faced full-on combat from the creation of the official Moral Majority movement.
I grew up with that hatred of who I am and it exploded in the 90s with Limbaugh and then Fox News and now it is a hatred so strong I really think they have lost sight of why they hate. They just know they do. They are repulsed by anything and anyone they deem liberal (though, like Archie Bunker, can tolerate loved ones even if we've gotten to the point we can't tolerate their hatred any more). It's pathological and so much bigger than politics or quaint "culture wars" now.
It's irrational and has become a full-blown cult with Trumpism, with outright dehumanization of liberals/progressives. I don't see how the spell breaks without everything getting much, much worse which is hard for me to fathom.
EDIT TO ADD: Steve Maurer's post above made me want to clarify that part of what they so obviously hate is the "love everyone" message -- no matter the skin color or religion or nationality. I agree with Steve that hatred of The Other, and us calling it out or rebelling against it, is at the root of their hatred of us. It's probably not so much an anti-war stance as the anti-war protesters not hating The Other as we're supposed to and thus seen as traitors.
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