Rusty, the thing you and most others under 18 never seem to look at in your arguments; at 18 you become Legally Responsible for your own behavior.
If you are immature and dumb after 18, YOU pay for it, not your mom. Until then, someone else pays for your mistakes.
Look at voting; you can read a lot about politics, stay informed, learn, even participate in various ways but you cant vote until you are 18.
Does that stop you from gaining knowledge? No. But no matter how mature or educated you are on the subject, you still cant vote.
The law says that replicas (as airsoft tend to be seen) CANT be purchased OR owned unless you are 18. There is no loophole.
Being mature and responsible means respecting the laws, for starters. All of them, not just the convenient ones.