The notion that 18 or 20 is some magical mystical number is completely absurd. Similarly, comparing a child playing airsoft with adults to a child being a soldier in a war with live munitions and actual death...well, yeah that's pretty absurd too. In this specific example, yes 10 is probably a bit young to be doing this, but if the kid wants to and the parents think he's ready, I don't see why he shouldn't be allowed to join up. Children understand and have a very clear concept of what is real and what is not real. If you're concerned about glorifying real war by letting a child enjoy pretend war, then I'm forced to ask you why it's ok for an "adult" to glorify war but not for a "child."
Either war is something to be dallied with or it is not. I've met a completely rational and well balanced individual whose parents let him play Biohazard at the tender age of six, so you can't actually convince me that there's a one to one causation between simulated violence and traumatic developmental ends. Furthermore, the assertion that we replicate "very closely" that basest of human acts leaves me dumbfounded. What exactly is "very close" about this simulation? We have to deal with none of the following: Blood and gore being expelled when we're hit with a bb, staying dead once you're dead, years and years of living as a cripple or with chronic pain because of something you quite likely had no control over at all
Airsoft is as close to real war as playing SOCOM on your Playstation is, and that's by design. We don't WANT our game to be a "very close" replication of war because even a "somewhat close" approximation of war is still ghastly and infinitely destructive. What we're doing is a game. That's why we have all this safety equipment and all these rules, because as everyone's mother has said, it's all fun and games until someone loses an eye.
I'm not downplaying the seriousness of what we do here; it's definitely true that things can go afoul in airsoft, especially when rules aren't followed. I recall reading about someone who injured his back falling out of a tree some time ago. There are very real risks we take, but we also shouldn't try to think that these risks bring us any closer to the real thing than playing a video game does. Child soldiering is bad because real war destroys real lives and steals real childhoods. Fake war does none of these things unless you screw it up pretty badly.
To get back to my original point, it depends on the kid, not on the kid's age. I've met people more mature at 14 than people I've met at 40. If a kid is serious enough to actually be fully devoted about safety and eager to follow the rules and show that he has the proper level of respect, and if that kid's parents, who supposedly know him better than any other person on this planet agree, then why not? Kids break bones and tear massive chunks of skin off themselves doing normal kid activities like riding bikes and using playgrounds, so I don't see how a properly run and participated in airsoft event is any more dangerous than that.
I should point out, by the way, that I'm single and have no children. I wouldn't be surprised to find myself more conservative in this respect when/if I do ever have one of my own, but being only slightly separated from my own childhood (some would say I'm still living in it), I don't think it's fair to youths in general to make a blanket assertion about them not getting it unless you throw in a few hefty disclaimers too. Again, it's definitely true that there's a point in our development where we can't handle this sort of thing, but it has far less to do with a number than it does with upbringing and good ol' genetics. My earlier statement about treating kids like kids probably should have been made a bit more explicitly. I meant to say that it's wrong to enforce pointless number-based limitations when a child is quite clearly ready for more responsibility and trust than they've been given. Please continue to keep your 2 year old away from guns and strippers, Fareast!
I think this is a pretty interesting topic, so sorry if I've tended to be a bit too wordy on this particular thread.