ON TOPIC:
I don't think it's cliche. I like the trope in general. Game of Thrones has its pros and cons, but one of the things it did really well was present two characters on opposing side sympathetically and then have them eventually clash and it worked like gangbusters pretty much every time. You'd hope against hope that somehow both could win. Brienne vs The Hound is probably my favorite example.
OFF TOPIC:
Actually PJ that's not completely accurate.
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Was that the reason for the war? No. The reason for the war was the same as the American Revolution. The south was sick of the north trying to tell them what they should do.
Lincoln was actually not against slavery (though his wife very much was). He freed the slaves to thumb his nose at the south and further prevent them from rising up against them again.
There's nuance here to be sure, but your summation isn't all that accurate either.
State's rights is and always has been sugar-coating it. The precursor to succession was the election of Lincoln with sub-40% of the vote, his shiny new Republican party's "stop the spread of slavery with the long-term goal of eradication of the practice", and the realization that the ability to politically protect and expand slavery for economic reasons had passed the tipping point. While individual states threw in a few secondary grievances in their articles, the primary reason for succession was perpetuation of slavery no matter how it's been danced around at the time or since.
Lincoln was late to the abolition cause and never 100% on-board, but he was quite clearly anti-slavery by his own admission in the 1850's prior to his election at a time when it politically was disadvantageous to say so. Just one of numerous quotes on the subject:
"I have always hated slavery, I think as much as any Abolitionist." - Lincoln, 1858 (Those same speeches do still present a lot of pretty awful racism by today's standards.)
I had a great history teacher in high school. These nuances were covered, though in brief. YMMV.