I think the letter is interesting not so much for the facts (which are not inconsistent with what one would find in the Border War accounts of Castel, Gilmore, etc.) but for the attitude:

"But they, fools like, would not heed, and sure enough we were ordered over to see to them" - they got what they deserved - justification for any outrage.

"Nearly every man in the county were traitors" - no need to be too picky in determining if individual residents are Unionists.

"I am afraid there will be more work than pay about it" - pay is a function of the mobile wealth in the region that can be appropriated for personal gain.

One can easily read too much into the printed word, but those were the interpretations that occured to me when reading the letter.