There is a very good book "Time and time again" by Ben Elton which shows why these "time travel" kills in the past will not solve humanity's issues. You can avoid one war by killing some people in the past, but you will not avoid other wars and conflicts. And people will never be happy. Nothing will be enough. An idea of killing people in advance because they can do something bad is a first step to totalitarianism where a small group of people will decide if your future choices are good enough to let you live.
So, the time travel ideas were good. But the political/moral message is really disturbing.
So, the time travel ideas were good. But the political/moral message is really disturbing.