My argument is that a 14 year old is a child. A fully developed adult is different. A 14 year old is one year into being a teenager, there's a difference. Legally or not, killing a child in a game isn't going to sit well with anyone besides a select few (like you.)
It went right over my head? Your argument is that it is a child, 17 is legally a child in some places. Derp right over YOUR head.
Well, America is the main consumer of games, and America considers adults at a higher age than most other countries. So they might go for the target audience's standard or go with a country that they expect a lot of revenue from's age if it's higher than other's. Making it 17 would be passable, but the game would still get banned.