[apatil]

Exploring your second point a bit more: if it were five billion lives rather than five lives being saved, most people's intuition would be that regrettably it's necessary to murder the one patient. Our intuition about this thought experiment transitions from deontology to consequentialism as the magnitude of the utility impact increases. There's something unarticulated about the murder that seems worse than five natural deaths, but not worse than five billion natural deaths.

Maybe it's the fact that the act would have a major negative effect on the surgeon, or that admitting a justification for murder other than self-defense could open the door to abuse causing widespread harm. Ie, maybe our intuition is basically utilitarian but is constrained by rights and rules to protect against risks that are hard to quantify.

[aeternum]

Yes, even from a utilitarian viewpoint, the prospect of living in a society that will murder you if there happen to be a sufficient number of people that require your organs is a dismal prospect. A utilitarian should also account for that very significant negative externality.

Many of these examples fail to take overall utility into account. The sadistic pleasure is another prime example. You must consider not just those who would enjoy the torture but also those that would be repulsed by it.

Same with the cookie. Rewarding a serial killer would make much of society unhappy. From a utilitarian point of view, giving the cookie to Mother Teresa (generally rewarding those who act kindly to others), is a very straightforward choice. The individual perception of cookie sweetness contributes very little to the overall utility.