Derp. I understand a lot more now. I totally misunderstood the "enemy". I thought the idea was there were people who were "traveling back in time in comparison to us". Basically their future was our past and vice versa. And they thought we were messing up "their" world somehow. But the actual idea is they are just people in the future, trying to "fix" the past because of pollution/global warming/whatever. Damn, now I need to watch the film again.
“Extinction is the rule. Survival is the exception.” -- Carl Sagan