Survival of the fittest. You imply moral implications, I say that to me... my life is more valuable than anyone else. If someone were to push that button, and I were to die, then I hope they make the best of their life with the reward they received for such.
However, I would not stop myself from pressing that button... as in this world your 'morality' is only held by a set number of people. In a Utopia, sure, I wouldn't press the button because I'd have no need to, nor would anyone else, and everyone would love each other. In today's world, I have to eat and live... I most certainly can't count on others to not make the wrong decision...
If morality was universal, your belief would be just and right, however... not all humans act on such rational beliefs, and are therefore prone to kill me first. Why should I be the one to make the right decision? What implicates me to be the better person when there is no ramification to my actions?