I think the fact Britain is a big 'M' monarchy blinds a lot of people to the fact that post ECW British Kings and Queens simply didn't have the kind of powers that are traditionally associated with a European crown.
Part of this is also probably to do with the American foundation myth that they were being 'oppressed' by the British King. When in fact they were being 'oppressed' by a partially elected representative body in the King's Name.
Thus the common thought (especially from Americans) about British Monarchs prior to Queen Elizabeth II, is that they somehow wielded absolute style powers, in one of the most advanced nation states of the era. And only reformed into being a nice quiet constitutional monarchy after 'murrica! showed the world the light of democracy after WWII.
The reality is though the British Empire did a lot of outright awful things during the 18th and 19th centuries, almost all of them where perpetrated by an elected government, bureaucratic institution, or private individuals. Not by some tyrannical King or Queen.