They were Calvinist oppressors by chance. By purpose they were the royal houses of Great Britain, who sought to end any chance of a Royal Irish challenge to their claims of total authority - as well as their claims of rightful authority.
Largely true. I emphasized their Calvinism chiefly to refute the notion that evil belongs to one denomination or another. Although I find the notion that Calvinism has that Catholics are not Christians, and non-Christians deserve whatever terrible things happen to them tends to lead to many horrible forms of self-justification.