"Objective moral values and duties exist." True, false or unprovable?
We know being exists. We know being is good, and non-being is not good, because if non-being was not "ungood", then there'd be no problem with all of existence being obliterated. But there is a problem with that, because otherwise being wouldn't exist in the first place.
This is a poor leap in logic that fails, and also commits to circular reasoning. All of existence could absolutely cease to exist and this would not change the fact that before the event of existence ending, that existence existed.
No moral premise has been invoked yet. I'm not saying "it's morally wrong to obliterate all being". It is a purely ontological point. I'm saying "given that being exists, it is ontologically wrong for being in its entirety to not exist/cease to exist".
So that's how I get good=being.
??? This makes no sense. You clearly state that you aren't making any moral premises, and then you... do it anyway? You go from saying it's "purely ontological" to "good=being." Why don't you try that part again, this time without skipping the in between steps. Clearly state in logical form how you get from [being exists so it's ontologically wrong for being to not exist] to [being = good]. (but remember to shore up your [first] statement because as I pointed out, it's not even true, being isn't automatically good just because not-being means being couldn't exist in the first place.
Moving along...
I'm willing to accept that Natural = Being. It makes perfect sense to think of the natural world around us as evidence of existence, and I'd rather not suppose that existence is an illusion because it leads to a pointless dead end.
But I see no evidence in anything in the Natural world that suggests there is a moral fiber ingrained within. In fact I'd go so far as to say that morality itself is a product of only a human intellect's interpretation of an emotional response. True, biology is required for these things to take place, so one can argue that Nature has proliferated Morality, but it no way suggests that Nature itself is moral.
For instance, a tornado striking a community and obliterating it. It is a sad event, leaving many devastated. Does this event mean that they deserved it? Did Mother Earth decide that it was time for them to perish? Of course not. It's a tornado, there's only scientific evidence that can be gathered, which will point to the low/high pressure convergence that led to the weather event.
There's no morality in Nature -except- for humans (that we know of, I won't discount the possibility of other species on other planets in the Universe).
So, I cannot agree that Nature = Good because I see no reason to accept that Being = Good even though I do agree that Nature = Being.
And because of this I cannot see the original question as answerable. As far as we know, there's no proof that moral values and duties (duties technically stem from values, so it's unnecessary to state them separately) - morals - exist objectively.