Agreed. I think it comes from a certain level of "emotional immaturity". Basically certain people have to literally visualize themselves as characters and take sides etc to enjoy something. So when a character is evil they somewhat see it happening to themselves. There's a friend of mine who hates any character who opposes the protagonist. Doesn't matter if the protagonist is a piece of shit themselves. He's also extremely emotionally immature.

Mind explaining this "biased" view of the plot? Seems like a bullshit statement to me but I'll listen to an explanation.