My impression was that the military guy went out at night because he knew he was in no real danger and he thought he was looking bad compared to the hippie. After whining all day about the guy's bare feet, he had accomplished almost nothing, while the other guy had built an excellent shelter and brought in at least something to eat.
They are, of course, playing up the conflict between the two guys, in standard reality show fashion. I don't know how well that will hold up over time. I hadn't realized that they would be rescued at the end of the first show. I thought it was going to be an ongoing situation. If they keep dropping the same two guys into different environments, I can see it getting old pretty quickly.