No, it's the perfect example because we can't help but rationalize a way to justify pushing it. If you now gave every single person that button, humanity would be extinct within minutes - many of them rationalizing that they're saving humanity.
This is the heart of where the saying that power corrupts comes from. It's not that power corrupts but that these sort of decisions are ones that will never be available to anybody without power. Yet for those with power it's not that far away from many practical scenarios. In other words, we start corrupt, but our impotence mitigates the relevance of that. Power just reveals our character.
And no, religious people are obviously not immune from this, but with a fixed set of values rationalization becomes far more farcical than without. The Bible's position on homicide, let alone for personal gain, is unambiguous. A person without any set of fixed values, by contrast, will have no problem justifying and rationalizing even the most egregious acts, so long as the reward is seen as desirable enough.
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To respond to your edit, consider that you're basically doing a version of the trolley problem where you have the choice to redirect the track from killing one person, to killing two, but you get a million bucks for doing so. And you're now arguing that this is the utilitarian choice. It's plainly a false rationalization, but we can so easily convince ourselves that it's reasonable. Our extreme strength at rationalization is humanity's biggest moral and ethical failing. [1]
[1] - https://www.youtube.com/watch?v=h242eDB84zY