True Blood's fifth season has seen Bill fall under the spell of religious fervour, which even led him to strike his progeny Jessica (Deborah Ann Woll).
Moyer insisted in a recent interview that Bill's devotion to Lilith (Jessica Clark)'s vampire gospel has led him totally astray.
"[Some are] saying he's evil and I'd say he thinks he's doing the right thing. But I suppose dictators always think they're doing the right thing," the actor told TV Line. "He's been lost and he's found something to grab hold of that he thinks is the right way forward."
Moyer went on to explain: "When you play a character you have to ask yourself, 'Can I make sense of what's happening here? Is this authentic?' And if you can sort of find a through line of authenticity, then you can play that beat - which might come across to somebody else as evil.
"[But] there were a couple of things that were tough to play, and one of those was [hitting] Deborah Ann."
Moyer further described how uncomfortable it was to shoot the scene where Bill slapped Jessica.
"We all have those moments. There have been moments that Alex [Skarsgard] and a couple of the other people have questioned this year just to make sure that the reason it happened in the writers' room works in our heads," he noted.
"You just have to make sure you're doing it for the right reasons. Of course I questioned it."
He continued: "Deborah and I adore working together and I wanted to make sure that this was the correct route. The scene in Episode 10 where Bill tries to explain to her that he's read this book and it's made a real difference - that was tough as well. That was a really difficult scene because we're seeing Bill truly believe, and I remember I had a conversation with Alex about it.
"And he was saying, 'What do you think? Are you okay with that?' And I said, 'I think I am'. Bill has this belief that what he is doing is right. Whether it is right or not we won't know until the end. But he is like anybody who goes into a cult. He's a victim. He's brainwashed. But... is it fun to play? Hell yeah."
True Blood's season five finale airs Sunday at 9pm ET on HBO.
Watch a trailer for the season finale 'Save Yourself' below: