Good point. If it has been hanging in a showroom for 5+ years, and is now in a humid area, it will take some time to stabilize, maybe a long time. If the dealer is a Taylor dealer, he should be well aware of Taylor's thoughts on the subject of guitar storage, and by ignoring their recomendations, well, that's just nutty.
The factory is powerless to help you if you won't let them see the guitar. Remember, their warranty only covers defects caused by things within their control. A dealer that dries a guitar out over the course of five years, and an owner who tries to rehydrate it over the course of a few days is outside their control.
It's possible you bought a lemon, and that you may have to live with it. There's every possibility, however, that the guitar will be just fine given some time and care.
Yet another hobby that is completely out of control...