With regards to Ireland, it's pretty reasonable to say that the Protectorate was simply following the path that their predecessors had blazed out and their successors would continue.
They may have followed the same path laid out since the beginning of the Tudor reconquest, but there are still a couple of massacres to take into account.
Also, in evaluating whether Cromwell was
a HP, it is not relevant whether he was following an established HP (horrible path, to use Atlas lingo). Something doesn't become less evil because it is normal or established practice. Its like saying slavery wasn't a horrible practice in all the societies in which it was a well established practice. If you use a non-relativistic scale such as FF/HP then the norms of the past become irrelevant.
You can use another scale and ask "was Cromwell a better ruler than the Stuarts?" and come to a different result, and a historian would always evaluate a ruler compared to his time, but that isn't really the purpose of FF/HP polls.