Now, you speak about 'Morally acceptable', but those that fly(actually ride) these vehicle KNOW THE SCORE. THEY ARE ALL VOLUNTEERS. These are ppl that are not going into this in a stupid fashion. They know what can and can not go wrong. Heck, If I can get a free ride on the shuttle, I will gladly take it right now. Why? Because I, like many ppl througout the world as well as all the astronauts, find it plenty safe and most certainly 'morally acceptable'.
They're volunteers who don't want to die. The fact that they volunteered doesn't mean they are willing to be test pilots for half-baked ideas. NASA's astronauts implicitly trust that engineers in charge of design are doing the best they can to keep them safe.
And here's a shocker: as an engineer, I don't care if you, the astronaut, have a death wish. I will not cut corners and knowingly make my design less safe just because you're willing to accept the risk, because if my rocket explodes on the launch pad due to a design flaw, I'll be the one responsible for the screwup that killed you.