I would define objective morality,as I suppose as something like this;
"equal consideration of equal interests of sentient beings per life time",
or to simplify discussion, feel free to say of human beings.
I think it is objectively wrong to have differrent judgements on identical cases. Of course, a moral nihilist would say he does not have different judgments, his life and suffering or pleasure is just as morally irrelevant as that of others. However, he still feels that suffering bad and pleasure good for himself regardless of what he says.
Now why per life time?
Imagine you have been asked before you came to life whether you want to be sent to live your life on earth, the advantages minus disadvantages of your whole life time should be rationally considered. The same should therefore be assumed in an objective moral theory, I assume.
The problem that I do not have an answer to is this:
If objective morality is true, and I still assume it is, how can separateness of persons and equal consideration of equal interests be both required for objective morality and impossible to achieve?
This is raising my doubt that something might be wrong about moral realism. Now I wonder if there is an answer from a moral realist to this problem.
E.g. you can not equally consider the interests of a terrorist and someone he is willing to kill.
Or you can not equally consider the interests of a lion and the animal a lion needs to eat to survive.
The is no point to meet in the middle, and suffering and pleasure will not be distributed equally.
Basically it seems that objective morality is demanding what is impossible in nature.