The Mayor was insanely in love with Faith but love has two faces.
We agree that love and hate are bassicaly the same, only their each others oposites, does that make sense, let me explain it a little more, love and hate differ only on the point that one is possitive and one is negative. So then if Love has two faces, hate has too and since Angelus and the Master were full of hate, well you do the math!
Okay I knew we would come at a point were I could find an answer to a why a character is partially good and partially evil, so here's another one of my theories.
Good and Evil are just as similar as love and hate
The Good-side loves doing good and hates Evil.
The Evil-side loves doing evil and hates Good.
Good both loves and hates, signs of both good and evil, so good is only half good and half evil.
Evil both loves and hates, signs of both good and evil, so evil is also only half evil and half good.
Freaky huh?
This problem will always remain as our definitions of good and evil are very poor. Nothing is really black or white, it's always grey. According to Tim Minear, in the US Tv Series special of SFX magazine, this is the theme of the Angel series, that not everything is black and white, but that's it's grey.