Your plane has just crashed into the Andes and you're stranded with no food. Because of this, you're left with the choice of either eating the passengers who were killed in the crash or to not eat them, but starve to death.
i am fully prepared to do whatever i have to to survive, and you are too, regardless of what you may say now. self preservation will kick in and change your mind when you've got starvation eating away at you, and food right infront of you.
A group of terrorists have captured you and have said they will kill you if you don't tell them where a family member/friend is. Would you not tell them and risk being killed, or do you tell them to save you're own life?
while i would eat a dead body to survive, i would not kill a friend/family member to save my own life. i would die to protect anyone.