(1) If the flourishing of conscious creatures is the foundation of all our moral judgements then saying something is wrong seems no different from saying that such and such an action will result in fewer, less healthy conscious creatures;
NOPE. I never said the flourishing of conscious creatures is "the foundation of all moral judgments". This is very common Christian apologist absolutist language (as if it is somehow assumed that we must have
some unalterable standard). I said (for me) morality is (at the very least) about the well being of human beings (and for some conscious creatures). I also followed that up by stating that that IF
morality is about the well being of conscious creatures then it is (at least to some extent) objective. Why? Because science (medical/psychological, etc) can tell us quite a bit about wellness.
however, when we condemn Stalin for the gulags it seems to me that we are actually making an 'ought' statement and not simply a statement to the effect that Stalin's actions resulted in fewer homo sapiens - how do you bridge the is/ought gap?
If I was attempting to bridge the is/ought dilemma (but I'm not) I would do so by arguing what morality is about. Again, if morality is about the well-being of conscious creatures (particularly humans), and science can tell us some things about that (provided that one wishes to be well) then it is not a leap at all to say how things ought to be.
(2) I think that we look very differently on the actions of various kinds of sentient creatures. For instance, if a pack of hyenas drives another species to extinction we don't set up a tribunal to investigate possible genocide. If that is the case then why do you consider it morally repugnant when another species of sentient creatures (specifically, a stone age Palestinian tribe) attempts to do the same thing?
As I just noted above, for me morality is about the well being of humans (not necessarily about animals but that can
be included). The bigger issue here, and I think it's where you (like most Christians) are hung up, is that I reject the notion of an "objective" morality (at least in the sense of the term in which most religious people use it). I see no reason, whatsoever, for thinking there is some moral "standard" somewhere that applies regardless of whether there are any physical/rational creatures around. On the contrary, the evidence I see is that there is us (humans) by which to make moral decisions. That is all. Thus (in general) morality is about us - and little if anything else.
(3) I want to know what exactly 'human flourishing' entails so that I know how to make good moral judgements. Is it just about concepts like health and sheer numbers?
This is another common Christian misconception - that you need some 'absolute authority' to tell you how it is
- otherwise you'll just feel lost and not know what to do. Why do you need me to tell you how you ought to run your life? Hell, why do you feel that you need some authority to tell you what is moral, period?? The cool thing about life (regarding human flourishing) is that much of it is up to you!
You get to decide what constitutes your flourishing (in many aspects) and what choices you will make regarding it. And you also get to decide how to treat others. It's not that complicated.
If you have some fear that if there is no 'objective' moral standard and henceforth there will just be chaos, or destruction, or meltdown then you're just deluded. Would you just start raping, killing, and pillaging if you didn't think there was an objective ethic/God somewhere? Your actions have consequences, regardless of whether there's a deity.
If so, then were the eugenics programs that the Nazi's pursued a good idea, in principle - after all, their goal was to produce 'healthier' homo sapiens was it not?
Uh, what? LOL. No it wasn't actually. Those programs were developed to create a "Master Race" and weed-out anyone who was deemed "unfit". But violating people's freedoms in such a fashion significantly diminishes happiness (and therefore their well being). Thus, I deem those public policies immoral.
In addition, as a normal male of my species I enjoy sex; so is polygamy ok? Seems to me that I could produce a lot more children if I had a lot more wives.
Personally, I see no problem with polygamy. If you can find multiple women who (by their own accord) are willing to 'share' you with other women - go for it. I see nothing immoral there as of now.