"And later in the century, as one phase of the conflict between England and Ireland followed another, the sins of Cromwell and his army in rooting out the supporters (both Catholic and Protestant) of the Stuarts in Ireland were used regularly as a stick with which to beat the English, albeit well over 300 years later, and as further proof that the Irish have perhaps the longest memories in the world."
For some historical context, start here: https://en.wikipedia.org/wiki/Siege_of_Drogheda
And as for the conclusion:
"The growth of British power and prosperity in the eighteenth and nineteenth centuries was in great measure built on those secure foundations. Cromwell’s part in leading the great change of culture was absolutely fundamental to that."
So Cromwell helped build the foundations of the British Empire, and that's a "good thing"? I don't know where to start, consider me triggered ;-)