Perhaps Jim, but Thompson said what he said, and he admittedly executed his fellow Confederate comrades for the simple reason that he wanted to put a stop to a specific virulent tit-for-tat feud that was going on. What tit-for-tat feud that was going on at the time was more virulent than the one involving the McGees and Catos, and what makes it more plausible that Thompson was inclined to kill some other group of Confederates rather than this one? The fact that the McGees are real flesh and blood people to us all and that takes it out of the abstract? And why would Thompson be more inclined to deal with a lesser virulent tit-for-tat feud while the bloodiest feud known to have ever occurred in the region was raging unchecked?
My thesis may be a stretch, but the alternative would be worthy of a Tom Clancy early post-Cold War tome, with American and Russian hit teams collaborating with a secret society and with all parties working toward the same goal--only in our story, it is Confederate and Federal hit teams cooperating with a secret society working toward the same goal. That alternative would necessitate that, coincidentally, at the very same moment in the history of time, two military hit squads were operating side by side in the same area if Arkansas--one was a Confederate/Masonic hit squad operating with impunity in the midst of 10,000 Confederates; and the other was a Federal/Masonic hit squad operating with impunity in the midst of 10,000 Confederates. Confederate/Masonic Hit Squad was tasked to assassinate Confederate Group #1, and Federal/Masonic Hit Squad was tasked to kill Confederate Group #2, and both teams got their men all at the same time.