Anything out of the norm is always discriminated against.
If something is geared towards a certain age group, you're always going to raise an eyebrow when you're not in the majority.
Another reason, a bit more indepth and psychological, is because people look at you like a parent figure. This creates a conflinct because I've run into several younger kids on this game who have a horrible family life and no sense of love at home. They log on Graal to escape their parents, or family. By you moderating the forums and acting sort of like a mother, if you will, you're the exact thing they're running from.
You and younger kids both take a break from reality by playing Graal, however, you interfere with some of the younger player's escape.