It's an eye opening experience. You'll never know the things you know if you don't do it. That being said I've had a lot of regrets about it. One thing you should emphasize to him is that it is a war machine. A machine meant for destruction. It masks itself as this idea of great good and protection but there are a lot of people profiting from big military spending, there are a lot of people that have a lot of different reasons for the things the military does and not much of it has good outcomes whether intended or not. While he's in there will be no stability. He will move and move often. If he does try to start a family it will make him choose the military over the family and it wont be a choice. If he comes from even a modestly educated background he will be caught off guard by the guys/girls that maybe had nothing at all. I guess it all comes back to my first statement that you can't unwash what you see/do it stays with you. For me, I now see that it is something that is extremly questionable to risk your life or well being over. It is not romantic, and while there can be heroic those are moments and not everyday occurances. And whatever he thinks it might be he will be wrong about. For all you or I know he could end up carrying boxes around and sweeping floors for two years. It's a broad spectrum that's very unpredictable.
This hits a lot of the points I have thought about. I don't want to try to talk him out of serving, but we want him to make an educated decision. Ultimately, we want him to be happy with whatever he decides to do. (college, job, or military)
He's a good kid, works hard and gets good grades, tries to help everyone (often without being asked)
He wants to be a Sniper instructor and is open to making the military his career. We've talked to him about having a backup plan, due to the limited number of those positions. In most cases, a parent never wants to squash a kids aspirations. Again, hoping he changes his mind on his own over the next 18 months.
I'm not sure if it's just my impression of the Marines. Family and friends that serve(d) in other branches have tried to direct him towards the Army or Air Force.