Is there a specific fact, letters etc. from the time you’re arguing against? From what I recall his barbarism was seen to stand out at the time in England and Ireland. He used it as a type of shock and awe, so when arrived at the next town they’d just surrender or flee.
Just that the subject is the politics of the time (i.e. what were the people at the time arguing about - what was that "legacy" they were looking to influence), and that modern authors are looking at things from a different perspective.
