Replacing Religious Morality

[MindForgedManacle]

Given that objective right and wrong does not appear to exist, and certainly does not exist in the practice of human affairs, would the burden not lie upon the person claiming it does?

How does it not appear to? If by 'moral' and 'immoral' you mean "that which is and isn't (respectively) conducive to well-being", I can safely say that there is in fact a standard of right and wrong that is applicable in human affairs.

Also, how are we defining 'objective' here, anyway? Even if a set of morals applied to all humans, that's still subjective on the basis of species. Does the definition of right and wrong change, depending on the mental capacity of the being?

The word 'objective' is really a misnomer here, because even though I can say certain moral actions are moral or immoral from within my consequentialist framework, that truth is still relative to the framework. The real term for it is moral realism.

And you're misunderstanding the word subjective I think. If morality only applied to humans (it doesn't), then all human actions could be scrutinized as being moral or immoral. That's no subjective. Limited in scope maybe, but then again defining anything at all has to limit the scope of what one means for the definition to actually mean anything.

Morality (on my conception) only makes sense when talking of beings who have the capacity to reason, and more importantly, to suffer. If something in question lacks either (or both) the capacity to reason or suffer, it's easy to see why giving it moral considerations - outside of its effects on things that can suffer and reason - doesn't make any sense. Rocks don't have moral considerations and it's easy to see why.

That's usually how we apply it in practice. We don't hold children to the same standards as adults. We don't hold animals to the human standard.

Children haven't developed adequate reasoning skills or knowledge of the world. We don't apply a totally different standard, we just don't hold them to be fully-fledged moral agents. The same for animals, except we don't really hold them to be possible moral agents at all. That's not to say that we don't think they are to be considered morally; of course we do. Their ability to suffer is the reason why. Ask yourself, why don't you (likely) consider it immoral if a lion kills other non-human animals? Is it perhaps because a lion lacks the mental capacity to reason about things as abstract as ethics?