TheIrreverend, I responded to your other thread to ask you questions to better understand your point of view, so I will let this part rest for now.
It still comes down to subjective judgements at the end. "Human flourishing" is not a well defined term that can be used to sort through the scientific knowledge. Do we value happiness, for example, or do we value persistence and survival? What if you have to choose between everyone being happy for their lifetimes and then the human race ending, or everyone being less than fully happy but the human race continues into the next generation? Can you say that someone is factually incorrect to value the survival of the species over happiness?
And even if you do objectively define flourishing you still have separate but equivalent situations such as flourishing at maximum rate for 5 years and then stopping, or flourishing at half rate for 10 years. Can you say someone is factually incorrect to value one over the other?
Aside from all the other practical objections, this theoretical one is for me the crux of the issue. Try all you will, you cannot define 'flourishing', 'well-being' or, as Moore puts it, the 'good' purely on the basis of scientific investigation. This doesn't mean you can't (theoretically at least) use science to help determine which actions will lead to whatever you proclaim the 'good' to be, but the definition itself is a judgment value. Unfortunately it's not easy to agree upon the nature of 'flourishing', otherwise the entire field of ethics wouldn't exist, and we'd probably live in a much more peaceful world (unless of course everybody agreed that the 'good' is the incredible adrenaline rush one receives after dispatching a foe in mortal combat - but at least we'd be in agreement).
Well, trivially, total nuclear Armageddon with every human being dying would not be flourishing. (Though, might be a utilitarian paradise as there is never any suffering). A 1984 or Animal Farm would also not be flurishing as the clearly the characters in those stories, especially those in the background, where not mentally healthy, emotionally stable, physically provided for people. I.e., in order to flourish people a confluence of factors including sufficient mental stimulation, a sense of control over their own life, a sense of safety, physical healthy, freedom from disease, sufficient sleep, contentment, and probably a bunch of other stuff.
I.e., you could construct a society where most people were in despair, exhibit learned helplessness and were malnourished. This is not human flourishing. But, we know the things that inhibit well-being: violence, lack of control of your life, not enough physical stimulation. But here is the kicker. We are starting to be able to tell how these map on to brain development and brain chemistry. So you can physically tell if someone's needs are being met or not by running them threw a battery of tests. My point in bringing this up is to say there is an answer that is objective. (Also, note, that these are different for different people. Some people need more intellectual stimulation than some, while others need to work with their hands more than most.
If it sounds like I'm talking about society's rather than people, you are right. But here's the kicker: If we organize a society a certain way the individual actions flow from it.
Eg., if you think you need to always work for the greater good, and that causing a little harm is okay if it leads to a huge benefit, you could kidnap random people off the streets to do trials of drugs or to find cures or new procedures for medicine. But we lived in that society people would be constantly in fear and it would not be leading to a proper chemical balance.
Your outlandish example would be a tragedy. But if he had a society that lead to this sort of situation often that would also not be a flourishing society. Maybe one day we will figure that out. And may one day we will have a grand unifying theory of physics. But that's not today.