I've been watching the tv series "12 Monkeys" which is similar in concept to the film.
Brief summary - an extremist group (the Army of the 12 Monkeys) release a virus which kills off most of the people on Earth. A scientist in 2043 (in the tv series) sends back a man (Cole) in time to 2015 multiple times to try and stop the virus being distributed (unsuccessfully - in the first series anyway).
Here comes the ethical bit: Cole has a friend (Ramse) who discovers that he has a son but if the plague never happens his son won't ever have existed.
Cole and Ramse argue that the life of a boy (or any one person) is not worth the life of 7 billion people (and civilisation).
I agree with Cole (stop the virus) but my friend says he would want to keep things as they are (7 billion dead) to keep his son alive/in existence.
It's always a shock when you discover that people don't think the way you do
