The scientologist freak kills the survivalist because the survivalist is rambling on about he is the "resistance" and how they will beat the aliens.
By the way, the movie is truly awful. Wish I had my 9 bucks back.
I felt like I was watching the latest made for tv movie about how the disfunctional family deals with the latest tragedy.
I was bored with the dialog about 10 minutes into it and the number of inconsistancys/impossibles(like buried machines for 1 million years) kept me wondering if speilburg was on drugs or off???
btw, if they could bring the machines a million years ago, why didn't they take the planet then?