To what extent is any given man morally responsible for any given act? We do not know.
I don't know if I've ever played a character who's close to me. There have been some elements of myself in different roles. Sometimes, I show one side of myself and then completely conceal the other.
Ultimately you want to do something in life that people will remember. And with Buffy, I did that. I don't feel like I need to achieve something. I just do it because it's fun. And that takes the pressure off.