In GWX sinking a hospital ship will end your career and get you shot.
http://www.subsim.com/radioroom/showthread.php?t=155686
Sailor Steve points out one of the great ethical dilemmas of warfare, if it is considered correct to kill one of the enemy, why is it not correct to kill them all?
If you cannot kill them all, how many can you kill? Who is qualified to quantify when enough is enough?
If you can legally kill the bomb-dropper, why not the bomb maker?
If one can shell a first aid post, as is statistically possible during any indirect fire program, sinking a hosptial ship differs only in scale and probability.
How does laying a mine that sinks a hospital ship differ from torpedoing one?
No ethical judgements are intended here, once the decision has been made to use lethal force to impose a political agenda it is very easy to have violence escalate and societal mores fall off the rails. In WW2 an errant 500 pound bomb that killed non-combattents was called a miss but in our enlightened 21st Century some would have the same thing today a war crime akin to the Holocaust.
That is why wars are better avoided than fought but if one needs to be fought, they are better won than lost. The winners get to decide when any particular action is "correct" or not. That may be unacceptable to some but it's the reality of war and politics since the dawn of time.
Answers to the above and other questions are entirely subjective, all any soldier/sailor/airman can do is make the best decision they can at the time and hope that those who presume to judge their actions can put it into the context of the event.
<Climbs off soap box while donning Nomex suit and body armour>