The good guys inexplicably start treating Emperor Evulz as though he was always on their side while Bob acts as the Only Sane Man.
Zig Zagged: Emperor Evulz's appearance and level of rationalization are constantly in flux, with fan opinion changing from week to week.
The fans react to Emperor Evulz in an appropriate manner based on his actions.
The fandom remember that Bob is the hero and Emperor Evulz is the villain, and do not create multiple theories rationalizing his crossing of the Moral Event Horizon. However, those who do like Emperor Evulz prefer him as a believable villain or as a sympathetic character without downplaying his flaws.
The author wrote Emperor Evulz as a believable villainous character, and the fans ask the author enough questions about him to know that Emperor Evulz was never heroic or was once heroic before turning to the dark side.
The fans prefer Emperor Evulz as a villain because they think that he's more believable as an antagonist than he would be as a protagonist.
The author has written something from Emperor Evulz's warped perspective and fans reacted to him in an appropriate manner based on his actions.
"You don't understand him! He's not as bad as everyone makes him out to be!"
"I don't think the squealing fangirls quite get what a twisted piece of work this guy is..."
Invoked: Emperor Evulz is intentionally presented as a charismatic person in order to enable him to convert people to the dark side.
Defied: The producers intentionally make Emperor Evulz repellent, physically unattractive, with no redeeming features, and cross the Moral Event Horizon in his very first appearance in order to prevent people excusing his actions.
Discussed: "Emperor Evulz's ability to make people excuse his sins borders on the supernatural."
Conversed: "Don't those people realize that Emperor Evulz is supposed to be the villain?"
The fans have a hard time reconciling the fact that Evulz is well evil with their sympathy and/or attraction to him or his likability, causing them to subconsciously delete the fact that he's evil from their conscious mind. As a result, they try to justify his actions to make him seems less evil & think that changing him would be so easy that all you'd need to do is show that someone cares about him.