If that's your argument, then we shouldn't trust them with the ability to vote, enter into contracts, or get married.

Only if we start from the premise that there is no middle ground between totally infallible and too stupid to take any responsibility.

I meant teenage boys. Okay, you have a really nice daughter, cute, sweet, pretty, darling, adorable, precious, a girl you have never been able to say "No" to, who has had you wrapped around her little finger since she was six months old, great student, cooks, sews, plays piano, great babysitter, loves kids, popular, etc. and at 16 falls in love with a boy 18 and wants to get married. You "trust" him with your daughter?

That little scenario aside, the claim in my statement is that the military doesn't just use the strong desire of teenage boys to be members of groups but exploits it. The exploitation is in basic training, etc.

It's a manipulation.

For voting, entering into contracts, and usually even marriage, the role of manipulation is usually much lower and the consequences less deadly.