"Prejudice and Pride"
Much like the previous episode involving Gilda ("Griffon the Brush Off"), "The Lost Treasure of Griffonstone" is one in which a more obvious moral is baited-and-switched with a different articulated moral.
Rainbow Dash's remarks early in the episode, in which she stereotypes all griffons as "jerks" like her ex-friend Gilda, seem that the plot will focus on, er, "dashing" Dash's prejudices into the rocks of reality and friendship.
In the process, Rainbow Dash and Pinkie Pie, the ones chosen to journey to the eponymous town, can be expected to find the eponymous ancient relic to fix everything. With a little friendship and a fancy trinket, hope will wash over the despairing land like one of their usual rainbow-colored wave motion gun blasts over the villain of the season.
But it's NOT Rainbow Dash who needs a lesson here. It's Gilda, and the others of her species, who suffer not necessarily from prejudices against other ponies...
They, and Gilda especially, suffer from a damaged communal pride. It wasn't the idol (or a love of gold) that brought the griffons together, but a common bond, a social identity. When the symbol of that identity was lost, they gave into despair and tried to fill the social void with INDIVIDUAL gains, resulting in the greed that manifested every time Dash and Pinkie asked for some help or some backstory.
Dash's prejudices were unfortunately confirmed. The griffons were jerks, but not simply "because" as she may have felt at the time. The pride in themselves as griffons was still somehow there, but bruised. And when Gilda crossed paths with Dash, she had to take that pride, and set it—her OWN pride—aside for the sake of her friendship.
And THAT was the moral—to set differences, pain, selfishness, and individual pride aside for the sake of, as Pinkie said "replacing it with something better," friendship, and love for your fellow man, er, griffon.
It won't be easy, and no rainbow blasts here, but Gilda and the others of her home can make things work... one day at a time.
