Rear Seat Belt problems of the 2001 Oldsmobile Alero

I was stopped for a red light; the car behind me was coming to a stop when he was impacted by a vehicle traveling over 45 mph which forced that vehicle into my car, pushing me into the vehicle in front of me. My husband was sitting in the rear passenger seat on the left side; his seat belt shattered and released him from the seat belt causing him to hit the driver seat. I sent an email to gm motors on my concern for this issue. They have since come and looked at the car and report it is ok for this activity to take place. Gm told my husband that they are not responsible for the problem and that our insurance can cover the replacement of the belt. My concern is that I have a child. How can I be sure I will not experience this problem again but next time to my child? gm refused to comment on this concern. All Oldsmobile Alero 2001 owners beware; the back seat is where the law tells you is the safest for children. If this is true, why did the seat belt malfunction? I am getting rid of this car. I will not support gm products if this is the responsibility they take in this issue. Which is none.