Not going to use a spoiler, as I don't know how, but if you're on the second page of this topic, you have chosen to read several of them, one more won't kill you.
There is good and evil in all of us, it is how we choose to act on them that defines us. If you don't believe me, think back. I guarentee you that every one of you has had the desire to do something quite detestable, like kicking a purse-dog, and all of you have desired to do something good, like giving a homeless man a twenty. No matter how breif the thought was, it was there.
To anyone who doesn't believe in the power of free will: since no one has any choice in what they do, shouldn't we elliminate laws because people don't have a choice, and so they cannot be guilty. if they don't have a choice, they aren't responsible.
As for the time travel thing, any time traveler has already changed the "past," so the past we know, is the result of any time traveler manipulation that will ever happen. Perhaps a time traveler put Hitler in power because someone who you've never heard of had the same ideals and purposes, but wouldn't have failed, because he was a better strategist, or maybe he would have fooled churchill and had Brittain on the other side of the war. There are more possible outcomes to time-travel scenarios than i can imagine. Every time I think about time travel, I think of a new way it could work. Maybe time will protect itself from change, maybe each manipulation will just create an alternate timeline, maybe time travelers would be in some kind of alternate space and would be unable to effect the timeline. the list goes on.