I've heard the BS Patent stuff. If you will read Al Gore's book you will get another slant on this issue from the standpoint of an environmental extremist fanatics view point. I personally don't believe that Dupont had squat to do with it. The product, after all, was continuing to make a profit. Why would anyone want to do away with a product that is making profit.
For those who may not understand how the manufacturing world works, large capital expenditures are made with the idea of being a long term investment. Once this money is invested, very little of it can be recovered to put into other ventures. Factories are built, large equipment and process investments are made and if the product is halted, the investment in equipment and development cannot be fully regained. Actually during the twilight years of a products life cycle, it is often very profitable because R&D costs as well as initial equipment and process installation costs have been recovered, so there is more margin to play with.
This is a situation where one political group tries to blame it on another. It's just like a fanatic to do something fanatical but try to deflect the bad part of the effect on someone else.
Have a great day,