This isn't quite a parallel, because it's easy to rent a babysitter but not so easy to rent a kid.
WDW is for everyone - but not every single thing in WDW is designed with every single person in mind. However, perhaps a compromise would be to have adult only nights at a particular restaurant, or at a specific restaurant having no reservations beginning after 7pm that include persons under the age of 16?
There is always a danger with trying to stereotype populations, such as saying there needs to be adult only restaurants because kids are noisy, uncontrolled, etc. I don't think people are saying that though. While there are many well brought up or naturally docile children in the world, all it takes is one or two kids in a restaurant (where there may be 100 well behaved children) having a melt down or behaving without good manners to ruin a meal the adults sans kids at the next table might be having.
People requesting an adults only meal aren't trying to impose their wish for a quiet meal on the entire population of WDW, they're just asking for one or two places. They're not demanding all kids behave perfectly for their own comfort. They're saying that they understand kids will sometimes be kids, and that's ok - but give us another option for those occasions in which our 'perfect' evening calls for the melt-down factor to be removed. WDW is the place of dreams, and not everyone's dream is to hold hands while junior from the table across the room Wants To Eat Cheerios NOW!
I think someone has already made the point that in some situations, it's not the behavior of a kid - it's that people want an adult atmosphere, where there aren't ten year old boys at the next table when you're having a romantic moment with your other half. It doesn't matter how well behaved a child is in this situation.
Please understand, we're not kid-bashing or trying to make those who prefer to always eat with kids feel like second class citizens. We have a valid reasonable perspective that some of the time it's nice to have an adults only atmosphere, and it would be nice if Disney catered for those sorts of occasions as well as for the many styles of dining they have already provided.