[Kozak]

If there were serious concerns they should have left them in orbit until they were able to send up some kind of rescue vehicle, whether it be another shuttle or a russian caspule, whetever. The non-military people could have been evacuated. They could have squeezed them into the space station. There was no need to bring the shuttle back until they were convinced that it was safe.

Columbia couldn't reach the orbit of the ISS.
It would take multiple Soyuz capsules to evacuate the 7 man crew, I don't even know if they have one on the pad, it's not like starting the family car.
The shuttle can only stay powered up for so long in orbit, the fuel cells have a limited capacity.

Maybe we can make some kind of arrangement for a standby emergency evac vehicle in the future, but keeping an "alert" bird would be a very expensive proposition, remember this is the first time in 100 missions it maybe would have been needed.

Space is a dangerous place, pioneers have always had to accept some very real risks.

[Dubh_Ghlase]

Each (unmanned) Soviet supply ship contains a replacement Soyuz escape capsule. They rotate the emergency escape capsule with each supply voyage. One was just sent, so they would have had 2 at their disposal (up to 6 seats?) to return most of the crew. They could have junked Columbia, returned one set and then another set on the latest capsule on the current supply rocket.

Or left the non-essential on the ISS and sent a minimul crew back, just in case.

There were other options...