The issue of gratuities really doesn't have much to do with what any of
us think is right, or what
we are used to paying in restaurants at home. It is what it is.
Disney restaurants are overpriced about 20% or so, but eating in them ensures reasonable quality (if not much variety) and usually very good service -- as opposed to cabbing offsite to Olive Garden or Burger King. The prices are what they are.
An automatic gratuity is quite common at destination resorts. Disney's union contract specifies an automatic 18% gratuity for all parties of six or more, regardless of method of payment. It also specifies an automatic 18% gratuity for all parties using the DDE discount card, regardless of the size of the party. That's a legally-binding agreement that Disney signed, and that's what the gratuities are.
If a customer does not feel the gratuity is warranted, they can certainly speak to a manager. Realistically though, the default answer is going to be that the gratuity is dictated by labor contract, announced on the menu, and that's just the way it is.
There are no mysteries about the gratuity; it's specified all over the place (
DDP brochures, menus, etc.). If an automatic gratuity is published as restaurant policy, and we then eat a meal there...we've agreed to the gratuity.
The sensible thing to do is to recognize the realities of the situation, and plan accordingly.