Yeah I realize that, but I still think they did a good job not selling it to you. Ratings are in place for a reason and you might think you're mature enough to play an M rated game, but there are definitely people out there that aren't mature enough, and they shouldn't make any exceptions. Your mother probably has her reasons for not buying you the game, maybe she doesn't feel like you're mature enough - the ESRB, game companies, and society as a whole has placed the responsibility and choice of buying M rated games in the hands of adults, and your mom is exercising her right to deny you the game.
Also fuck yeah Charger, GO LAKERS!!