What is the purpose of NASA? Is it to develop new aeronautical and space technology (involving dangerous flight testing and spaceflight), or is it to cower in fear? There is no such thing as risk free spaceflight - never has been and probably never will be. If zero risk is the goal, then ground the Shuttles and any other crewed vehicle. Forget about flight testing, too.

Go to NASA's own website. On the very first page, it says NASA is chartering a bold new course into the cosmos, a journey that will take humans back to the Moon, and eventually to Mars and beyond.

How, pray tell, will they find the courage to do that if they're afraid to launch humans into non-ISS compatable orbits? Would it be dangerous to send a Shuttle to repair the Hubble? Of course - it'll be just as dangerous as all the other times they did that or flew to somewhere other than the ISS. Why is it suddenly too dangerous to fly such a mission now? Is the Shuttle is really that unreliable, or has NASA lost its guts? If the Shuttle is that unreliable, then ground it and stop wasting money on it. Take the $15+ billion a year that NASA gets and hire private companies to fly the missions.

Go read the National Aeronautics and Space Act (PL 85-568) that established NASA and ask how NASA can do any of that without risk. If we're going to send humans into space, we have to accept the sad fact that some of them are going to die. The astronauts are willing to accept what they consider reasonable risks, and they're the ones who'll do the dying when bad things happen. I respect their judgment on the matter.