Well, I’ve had a neighbor claim I was doing things on his side of the property line, which he placed in the middle of my driveway. For him, it was a property dispute. For me, it was the ravings of a not-quite sane person. Think of it that way.
You are right, it was not a trade dispute, but the raving slave-owners would say whatever they could to justify their actions and make it sound noble. Much like Putin says he invaded Ukraine to “save them” from “embedded Nazis”. For Putin, it’s a mission of peace. For everyone else, it’s an unjustified invasion.