That's not what they mean. They're saying Disney should make a movie with a homosexual (I assume that's what you're implying) couple so that kids are introduced to the topic early on and it becomes normal to them. That way, they aren't prejudiced and ignorant when they grow up.
I've heard it in many contexts, primarily homosexual, but also others like interracial relationships, ones with overweight women, ect. I see your point, but I don't think it I'd Disney's job to instill values. Also, if anything, I don't think we should be idealizing finding a prince(ss) at all. I don't think people should be socialized into thinking they must find or be in a relationship. I think such ideas are responsible for many people feeling insecure about how they look or act.