I will have to see the movie myself, but her description makes it sound like that is not the case in this movie, that there is no underground warfare because Cruise kills the Robbins character who wants to do that.
As I said, it's been a while since I read the book so I cannot say with any certainty how accurate that is. Much as I hate to admit it, I will probably go to see just so I can make my own assessment.
IMO he killed Robbins because he was unbalanced and would not shut up, and he was putting Tom C's daughter in danger. It was just the two of them, and Tom C's character realized that they couldn't fight the creatures themselves. While Tom C was no hero to start off with, he showed he would fight to protect his daughter.
If anything, this movie should be an example to people that it takes more than two people in a "cave" to fight something so powerful.