Tire Sidewall problems of the 2002 GMC Sierra

I had to purchase four new tires for my 2002 GMC Sierra on 10/2/03. Firestone in martinsburg, wv advised me that my truck tires that gm placed on the truck that was ordered new were not suitable for the weight of the truck. The sidewall of the tires were very weak. I am concerned that there are other trucks out there with the same problem. I went to the dealer who will not assist me with this issue. I sincerely hope there have not been any accidents due to this problem. Can you investigate and make sure the problem is resolved if this is not just an isolated incident.