I think the abolitionists (who's modern ideological descendents are today regarded as liberal kooks) hated the South, but I think most of the normal people in the North did not hate them until animosity was ginned up against them.
I think once your side declares war on someone, it becomes natural to view them as horrible monsters, because that is one of the ways people cope with doing terrible things to them. We've done it in pretty much every war.
I think much of the subsequent hatred of the South is a consequence of the need to feel vindicated and reassured for what was done to them. This is why in these debates, the people arguing on behalf of the Northern side invariably try to force the discussion into one about slavery, because this is the area in which they can feel both justified and morally superior; A powerful combination of emotions which many people cannot resist.
When the discussion is forced back to the idea of "consent of the governed" and framed in what was the normal social standards for the day, they are not so comfortable with it, because it does not clearly support what they would prefer was the truth.
Unlike the Nazis, the Old South embraced individualists, like Thomas Jefferson; other Faiths, like the Jews it elected to the U.S. Senate; Officers, who designed their own uniforms; even, despite the vicious lies of today, a level of goodwill between the races, which really did not exist in the rest of the Union.
It occurs to me that this "individualism" might be quite objectionable to the sort of people who want everyone to obey a controlling authority, especially if that controlling authority furthers the interests of people behind the scenes for which the controlling authority insures their prosperity and continuing power.
I have come to think this is the dynamic at play regarding the masters of the Media.
How many of the South haters, today, are even aware that Stonewall Jackson taught a Sunday School class for young Negroes in his neighborhood; that the song "Carry Me Back To Old Virginny," was actually written by a Negro song writer, from New Jersey, celebrating his love for a Virginia girl. (Unfortunately those Virginians who took it down as a State song, in response to an earlier hate driven attack on heritage, didn't know that either.
None of that is useful to them because it does not further their narrative. Therefore they don't want to hear about it or contemplate it.
Those who have revived the hostilities, post 1909, are a new breed of Jacobins--admittedly picking up the remnants of the former South haters--as in the founding of the NAACP. Or if you prefer, a growing collection of Marxists, Fabians, etc, who like other Marxists, Fabians & Nazis, abroad, have picked up the Jacobin egalitarian mantra.
All such groups share a strong compulsion for "uniformity" of thought; which after all can be a central element in the need to pretend that all of us are equal--even interchangeable.
We are now entering the phase where Jacobin mobs tried to destroy all the rudiments of French culture.
Contrast Booker T. Washington's picture of race relations in the Old South with the distorted narrative being pushed in Academia, over a century later:
Consider Calhoun--the most famous voice of the Old South's-- actual Libertarian views, with the way the Old South is now being falsely depicted:
Consider my personal take on what is going on: