The problem is that the military serves two purposes. While recent governments have largely used it as an offensive force, it also serves as a defensive force. Most of the folks that I know go into the military because they see it as a defensive force and want to protect their country and the freedoms of their fellow citizens. Very few of these people are sources of violence any greater than any other people their ages except on the battlefield.
However, another reason for folks entering the military even while being anti-war is the the U.S. military is one of the few work places where races, ethnic groups, etc. are very close to being given equal opportunity, so folks from groups that have a hard time “making it” in the outside world use military service as a ladder to climb to a higher social and economic status. They go in hoping to serve only in a defensive position or ideally under peace time conditions to get training and a boost in education and experience.
It would be different if Americorps, the Peace Corps, or an equivalent peaceful service option were available to accept these same numbers of folks that end up going into the military. But the funding and infrastructure is not there.
In the past, some folks went into the Reserves or the National Guard or even the Coast Guard to get these same benefits without actually making war or serving on foreign soil, but all of these people have now been turned into grist for the mill that is Iraq, so that doesn’t work, either.
On top of that, the military recruiters target the young and uninformed, recruiting directly in high schools. How many 17 year olds are really able to make an informed decision and foresee the ramifications of serving in order to get money for college, or training in electronics? Not very many.