You are saying that my argument fall short because it concludes that there is no objective morality. With this you could be saying one of the following 2 things:
Either you know for a fact that there is objective morality, and an argument disproving that fact must therefore be false, in which case I would like you to present the evidence or theory behind this fact.
Or you are saying that my conclusion is wrong because you would want there to be an objective morality, ie my conclusion is wrong because you want it to be wrong. I don’t know if this is what you are saying, but I if it is, I don’t think thats a logical standpoint.
Now to your question “upon what basis can we declare any action RIGHT or WRONG?”
I don’t think we can declare actions right or wrong. I can declare actions right or wrong, and you can declare actions right or wrong, and if our moral framworks are reasonably compatible, we can have succesfull peaceful interaction.
My moral framework is a result of my upbringing, my political views and, to a quite large degree, my biological composition. That is the basis upon which I, not we, declare actions right or wrong.
ps. I hope this does not sound to unfriendly. English is not my first language, and my tone might be more harsh than I mean it to be.