re: Probably not surprising.
The former anti-war hippies were probably among the 50% who didn't recommend their kids consider the military even before the Iraq war. It's the 25% who supported military service for their kids until 2003, but do not anymore, that you should be concerned about.
Given that the highest % of the population who identify as Republicans are in the age brackets likely to have high school kids now, the current numbers mean that even a sigificant fraction of GOP-voting parents recommend against military service for their kids.