We know full well that the death of a third Shuttle and its crew will lead inevitably to abandonment of America's human spaceflight program.
Isn't it through events like catastrophes that the most important decisions are made? I'm pretty sure it would galvanize the energies for a new manned space program. After Apollo 1, the Moon became much more familiar than it ever was. After Challenger, a new and better shuttle was built on time and within budget. After Columbia, NASA's goals were re-directed.

I'd rather wait a very long time to see another Shuttle launch than to have to go through the personal and national trauma of seeing another one lost.
We have unforrunately no way to know how safe the shuttle is until it flies. True, there certainly are systems that have been unnecessarily tripled, overchecked while others have been overlooked and forgotten.
It would be better to design a far less complex spacecraft.