This is the very reason that NASA is developing robots to take the place of humans in space. See these sites:
http://en.wikipedia.org/wiki/Robonaut
http://robonaut.jsc.nasa.gov/default.asp
Quite apart from the fact that in space, robots would be utterly superior to humans, and it would cost only a tiny fraction of the cost to design, launch and run a robotic mission compared to a human mission, having robots in space instead of humans removes the possibility of the dreaded scenario that you describe.
If a manned mission gets into an emergency situation, billions of dollars will be risked on a rescue that may itself turn into a disaster and fiasco. Then someone has to make hard decisions on what to do next. Then finally there would be an outcry from the media, religion and every nutty creed and sect under creation. Space exploration itself would be faced with extinction.
On the other hand if a robotic mission gets into an emergency, the robots simply continue until power runs out at which point they are switched off. The cost of the mission gets written off, lessons get learned, and NASA tries again with a redesigned mission plan. The situation is no more tragic than the failure of missions like Mars Observer, or any of the shots in the Ranger series.
So since NASA is aware of the risk to it's very existence caused by manned missions, it has wisely decided to pursue the development of humanoid robots to take the place of humans in space on all foreseeable future missions.
Cheers!