"Looper": On Time Travel, Suicide, and Sacrifice

If you could go back in time and assassinate Hitler when he was still a child, would you do it?  You would have to kill a child who had not yet committed any of the atrocities Hitler would eventually commit, so your victim would still be innocent. On the other hand, by that one act you could spare the lives of millions of others.  Would you be justified in doing so?

What if you found out that young Hitler was full of fantastic potential for good and terrible potential for evil?  Much to your surprise, he was an exceptionally gifted young man with the potential to either make or break the world.  Unfortunately, a devastating psychological and emotional blow made him eventually decide to break it. If you knew who the perpetrator was (though no crime had yet been committed), and that by killing him you could stop the future atrocities of the yet unscarred Hitler, would you be justified in killing the perpetrator who made Hitler a monster?

What if you discovered you were the perpetrator? And what if the only way to stop the Holocaust was to kill yourself?