Someone put up an article the other day where they were talking about some story that followed the bad guy from some other story and there was that whole 'every bad guy is a good-guy hero in his own head.'
Yeah - that's bullshit.
People have this terrible habit of thinking that only they are real. That everyone else, everything else, thinks like they do, feels like they do, believes like they do. They fall for that tired old saw that 'he's only evil because X happened to him, and you'd be evil too if X had happened to you!'
Yeah - that's bullshit too.
Bad people know that they're bad. They know that what they're doing is wrong - they just don't care. They either feel they can get away with it and not get caught; or some soft asshole, who believes the above, will go 'aww they didn't mean it' and will either let them go or let them off with little to no punishment. If you've ever raised children, you've seen this behavior a thousand times before. Your child (or even your pet if you have smart enough pets) knows that they're breaking the rules, that you'll be mad, but they figure that they'll either outsmart you and get away with it, or you won't punish them.
For those of you who don't punish them - congratulations! One day your child is going to have the boom lowered on their head and they're not going to like that! You've done a lot to set your child up for failure or worse yet, a nice trip to one of those lovely state maintained facilities. But they're not really evil, they're just stupid, lazy, and self-centered.
Now let's talk about the evil people. I have had the experience of knowing more than a few of these over the course of my life. These people know, when they do wrong, when they rape or murder, or do worse to someone, that what they're doing is wrong. Evil even. Guess what? They don't care. Hell, not only do they not care, but some of them even get off on it. You see, to them, the rules are for you, not for them. They can do whatever they want and if it hurts you, so what?
They're not sociopaths, oh no, they understand feelings and they socialize quite well. But your little rules are meaningless to them. What's right and what's wrong is what they decide is right and wrong. And that's always what's right or wrong for them, or their friends/family, if they feel close enough to them. Take smoking pot. A lot of you know it's 'wrong' but you still do it. You look at the laws and say 'eh, I'll do what I want, because I want.'
Well most killers or vicious abusers feel the same way. Oh they know what they're doing is a lot more serious than smoking pot, and they'll approach it with a lot more care. They know it's wrong, they know it's even evil. But they don't care, because they're benefiting from it in one way or the other. You are meaningless to them. Or maybe you mean something to them, but this means more and they're sorry they're going to kill/beat/rape/cripple you, but they're going to still do it to you and move on. Because they're evil, they're perfectly fine with being evil, and they don't make any bones about it.
Are they heroes in their own story? Yes. But they're not the good guys, and they know it. People don't join certain gangs out there to be good guys. They join to be evil guys. The bad guys. There isn't some 'incident' that happened to them and made them decide suddenly to be bad. I've had some very nasty things happen to me. Terrible things, soul crushing things. I didn't decide to go out there and suddenly become a violent or vicious man because of it. Same for dozens of people I know personally and millions more I don't. My name is legion when it comes to something like that.
There are a lot of people in the world who don't care what the laws are or what they say, but are still good guys. They're good because they were raised with a moral code and they believe in it and strive to do good things and good works. Those people exist regardless of what the law says. Regardless of what bad, nasty, evil, or terrible things have been done to them.
The same is true for those who only seek to do evil. They know what good is, what right is, they just have no desire to do those things for a lot of reasons, not all of which come down to some sort of 'mental' disease. Most of them are perfectly sane. Many of them have also suffered some terrible thing, but it didn't change them, they may use it to 'justify' why they do certain things, but that's just a lie to lure you in so they can get what they want from you.
Don't try to explain evil away. Don't try to rationalize it. Your only real choices in life are to either kill it, move far away from it, or leave it clearly impressed that if it fucks with you, it will suffer more trouble than it's worth. Sometimes you can respect it, but odds are you'll never really understand it.