Does a wrong thing become right when everyone would do the wrong thing?

To kill an innocent person who poses no threat to us and has done us no harm is the wrong thing to do. Nonetheless, given the right incentive - saving our own life, saving the lives of our children - virtually all of us would do it. Few of us are so committed to theoretical philosophical positions about right and wrong that as a practical reality we would allow our families to be killed over them. It is easy to imagine the circumstances in which each of us would behave wrongly: does the fact that all of us would do mean that it is no longer wrong?