Bill Nelson, for one. Other astronauts. And the press conference this very day, morning and afternoon.
So Bill Nelson and others asert that the Columbia shuttle could not have sustained 14 days in space from launch to reentry? According to NASA's webpage the craft was scheduled to stay aloft for 17 days (Jan 16 - Feb 1).
http://www.nasa.gov/columbia/mission/index.html
Your sources are therefore wrong when they claim nothing could have been done. IF NASA had erred on the side of caution and acted they could have been saved. They did not and therefore liable.