Brake Grinding Noise problems of the 2003 Chevrolet Silverado 1500

My 2003 Chevrolet silverado truck started making a loud grinding noise from the rear wheel. The vehicle only has 28,000 miles on it and has only been used for transportation of passengers and light hauling on occasion. I pulled the rear wheels and noticed the brake rotors and calibers excessively rusted to the point that the shoes where not contacting the rotor. The local gm dealer told me it was not under warranty( len stoler Chevrolet in westminster MD. ) I replaced the rear pads and had the rotors turned down and also replaced both rear calibers with new ones and still the noise is there. Also the brake pedal is very soft and almost goes completely to the floor even after numerous beedings of the calibers . There is no air coming out of the bleeders. The anti lock brakes apparently don't work because the wheels lock up and slide when you press hard on the brake pedal. This truck has been a nightmare when it comes to these brake problems. The brakes still don't function properly and nobody can tell me how it can be fixed properly since it clearly is a engineering design fault by general motors corporation many people have to get hurt or even killed with these faulty brakes before gm is held accountable for their faulty product? this vehicle was taken to lenstoler Chevrolet under warranty for the brake pedal going to the floor on 10jun2005, where they replaced both rear rotors because they where rust pitted and out of round with just 20,136 miles on the vehicle.

: the contact stated while driving 10 mph and under normal braking conditions, there was a grinding noise in the left front brake. At the last second, the brakes pulsated and the pedal became hard to depress. The vehicle was not taken in for service.