This is a serious question and not meant to be sarcastic: How much did you play in EA with Shadowheart in your party?
She was with me all the way in two of my act I play-throughs. Adolf Hitler liked puppies too you know.
First off, the hitler joke made me chuckle out loud, so thanks for that
Second, I don't want to delve into any particular real world examples, but there a plenty of people who follow intolerant/evil religions and are not themselves evil.
Third, I would like to understand what exactly Shadowheart did in your playthrough that screamed "Evil!", because I didn't really encounter it. Other than a couple selfish moments, she has definitely erred on the side of nice/good. Heck, on my evil playthrough I had to work to convince her that killing the druids was a good thing, she was not okay with it by default. Which I think speaks to Larian's goals of us being able to guide how our companions think and feel about us and the world.
