While I am normally in no rush to link Vox, I do think this is a pretty good piece about why the High Sparrow was so hated by the fans: http://www.vox.com/2016/6/30/12055374/g ... -hypocrisy
Key excerpt:
The High Sparrow was hated because we fear our fellow sinners less than we fear the naming of our sins. I say that in religious language, but I don’t need to: We don’t fear brutality and vengeance half as much as being found out as brutal and vengeful ourselves.
That disgust with the Sparrow, that visceral, gut-rolling discomfort beyond the ordinary fun of hating a fictional killer? That is the terror of a light turned too harshly, the question of whether, deep down, you ought to be ashamed of yourself, even if the person shaming you is just as imperfect as you are. Especially if they are as imperfect as you are.