I believe we are diagnosing the problem incorrectly. Age is a very limited factor when it comes to determining the demographic of trolls. I think that most of the trolls actually come in the form of literate adults. Little kids should be able to play, they have just as much right as adults do. In addition, it falls onto the player what kind of spirit he/she brings to the game, not their age. I don't like the idea of a pay4play, considering most of my friends and I were initially compelled to play by its free4play format. In addition I can not imagine it will change the culture of interaction between players a bit, even by your logic.
Even by sight of the champion menu, I'm anxious and worried to meet my players. It is becoming increasingly rare to find a decent group of allies. I really want to start playing with friends to ward away any danger of meeting ill spirited players, but it seems to limit the development of teamwork and cooperation I can build as a player.
You could have just as easily left out that last line and your point would have gotten by without the nonsense. It's a matter of choice when it comes to how much we write or say to another person. When we invite hostility to a conversation or we continually perpetuate and normalize it, it will show up much more often in our community which goes against the nature of this particular thread.