I trained with the military. I learned how to shoot, throw hand grenades, conduct combat in basic squad formations, protect myself and others against biological attacks, and so on. Just because I served does not mean that I am a "murderous wack-job".
Because of thier very nature, the military services (as well as law enforcment agencies) are a collecting area for people who CAN be disposed to performing violent acts. We were always on the lookout for people that exhibted this behavior and dealt with individuals who did.
The military exists to protect your rights to speak out against it and the government it serves. You can't blame it's training techniques since it serves it's purpose; we can have this debate without fear of retribution from our government. You can't banish or blame it's members simply because the military teaches them how to shoot a weapon. Real weapons are what make us an effective and deadly fighting force.