Are childhood bullies "bad" kids?

Yes, they are. And usually they come from 'bad' parents. Some of them may even be proud that their kid is the bully.

At the age you're referring to children are too young to know what they're doing, or why they're doing it. Most of them will grow out of that kind of behaviour, but those who don't have a genuine problem.

Yes.
And I don't blame their parents entirely.
I had a rough childhood, I went to school emotionally hurt.
But I never beat up some innocent person out of inner turmoil.
They know what they're doing, and they know its wrong.
No and's, if's, or but's about it.

It's sad how many people think "bad childhoods" and "bad parents" can excuses them from being decent human beings.
Excuses, excuses.
Reguardless of them, we all know right from wrong, and we all have the ability to choose one.
Bullies choose to do wrong.
So they're bad kids.

Bullies are usually 'bad kids', yes. The kind that purposely hurt small animals without feeling bad about it. The kind that grow up to become serial killers.
Abused kids more often than not will withdraw and try to be invisible or only harm themselves.
Insecure kids are not the ones with truly malicious behavior, just lash out to amuse themselves and feel greater than another temporarily.
Really, it all depends on the perspective of the kid being bullied. Their bully may be getting picked on from another one or group. We're just hairless animals.

I don't really think you can generalize. Everyone is different, it depends on the situation and what they're doing to constitute bullying. I know that I did some things in high school that would be 'bullying', but when I look back now I just think I was really immature. I would never do anything like that now.
Kids are kids. They're still learning what's right and wrong and who they are. Of course, some kids have problems, at home or mentally etc (psychopaths do come from somewhere), but I think there are many many factors that come into play before we can brandish them all 'bad'.

i would say a lot of them are acting out things that they are experiencing and just don't realize the wrong in it.
I was a school bully, but i bullied the bullies.

yes.


one can find excuses, explanations, shared guilt, etc. doesn't matter how they got bad, they are bad.

No they just were never told its not okay by adults to be that way. Most kids behavior stem from the adults around them.