RAVE started out like this too. Light hearted on the outside, but as the series went on it hit on darker material. Same pattern Hunter x Hunter, Naruto and Bleach followed as well. It's fairly standard in the shonen genre.Originally Posted by Idealistic
I can't say the same for the anime as it continues, but Fairy Tail has touched on darker subjects already, like with the enslavement of an author by Everlue, alluding to the wealthy abusing their power when they can. Same goes for the slaver in the first episode. There are clearly wizards that abuse their power. The anime has cut some of the harshest material already (as Archie pointed out) since I think they are going for a larger (incl. younger) audience, but I'd give it time.