The survival instinct is stronger than any human force I can think of, except perhaps a mother's protective instinct. People have cannibilized in order to survive, in several documented cases.
Anybody who answers that they would not do so is mistaken. You would, any human would. When you feel the fear of death upon you, you have no idea what you will do, until you are in that situation.
That being said, eating someones feces would not save you from starving to death, think about it. The only way is if someone held a gun to your head, in which case you could probably figure that they didn't want to kill you really, just to see you eat ****, or that they were so twisted that they were going to kill you anyway.
In any case, humans have, and likely always will, do much more repulsive things to survive.If you say that you would rather die, I say OK, Try It Sometime. You will be surprised.