crack on rear door of mountaineer

I have expierenced a crack in the rear door of my 2003 Mercury Mountaineer, I went to the dealership and spoke with the service manager, he said that there have been several complaints do to the stress of exspansion and contraction and it isn't covered by the company.. I will NEVER purchased another Mercury or Ford product again. The told me that they would give me a discount for a new

door. I don't think that I should be responsible for any of the cost because of the manufacturers product malfunctioning, no one told me of the mishap when i bought the vehicle brand new in 2003.