'Utilitarianism is the best approach to solving moral dilemmas'

Utilitarianism has in its favour a naturalised (definition-deriving what is good from what is natural), common-sense view of ethics. By associating what is good with what is pleasurable and what is bad with what is painful, it grounds ethical decision-making in intuitions people already feel and that lead to easy decision-making. It also helps to solve tricky moral situations with its focus on maximising pleasure. For example, one patient who's organs could be harvested to save the lives of three patients and we should do this because the pleasure felt by the 3 outweighs the pain of the one.However, there are three challenges to both these strengths of the theory.Firstly, according to Hume's Guillotine, we cannot derive an 'ought-from-an-is'. In other words, we cannot derive what we ought to do, a normative principle, from what is given in the natural world, what is. For example, humans eat meat in nature. But we cannot move from this to the descriptive claim that we ought to eat meat. Similarly, just because humans experience pleasure and pain we cannot derive from this that pleasure is good and pain is bad.It is problematic to associate pleasure with pain for other reasons. Genghis Khan got great pleasure from murdering, raping and plundering. Does this make his actions good? A utilitarian could retort that his pleasure would be outweighed by the suffering of his victims. However, in my opinion, this is not plausible as we can imagine a scenario where some hypothetical tyrant always gets more pleasure than his victims feel pain, and therefore his actions would be just. Further, utilitarianism would absurdly suggest that the more pleasure one gets from their evil acts, the less bad those actions are. Someone who coldly kills someone like a soldier in combat is 'more bad' than a psychopath who enjoys their killings, who's actions are more 'good' as a result. Lastly, the example of the doctor harvesting the 1 to save the 3 could lead to immoral results in other situations. Suppose an elephant is being humiliated in a circus and is clearly suffering, or someone is being tortured in front of a Roman colosseum, yet the crowd is sufficiently large so as to outweigh the suffering. A utilitarian might retort that the intense suffering of the elephant outweighs the little pleasure the crowd gets. However, with its cold and mathematical approach to decision-making, we can construct a similar counter-example to the Genghis Khan case, whereby the crowd is maximised and maximised to the point whereby it is a mathematical inevitably that the number of spectators and the pleasure they get outweighs the pain the one feels.