Objective morality as a proper basic belief

[The Grand Nudger]

'Wants to do the moral thing' in no way compels people to act. While harm can certainly judge a situation, can it compel people to act?  

People personally desiring something is the singlemost decisive form of compulsion there is...Steve........  

When that fails, can harm compel someone to act?  Why, it certainly can.  You pull your hand back from a fire, don't you?  That's the point of shame and societal pressure and even law.  To put the fire to your unmotivated feet.  That's the point of hellfire, as well, ofc. 

Ideally, it won't come to that, your fear of being harmed by immoral people in an immoral society, and natural tendency towards reciprocity as a human being should be enough.  For most of us it is.  We don't want to do some bad thing, we want to be good people, we don;t find ourselves charged with moral (or legal) crimes with any sort of regularity..and when we do we face punishment or seek to escape it.   

But, for some people, none of this works.  If you're one of those people we'll put you were we put such people. Padded cells, or the grave.  The final and most ultimate form of compulsion. Do what is right or be killed.

In any scenario you have to ask the question why. In order for harm to be the foundation, the answer to the question why has to be that harm is wrong (an explanatory ultimate). In the example of murder, asking the question why is it wrong does not simply stop at because it caused harm. As you agreed earlier, you have to apply moral reasoning.  The why (the explanatory ultimate) is rather:

1. That humans have intrinsic value (we don't call killing a rodent murder). 
2. That we have an inalienable right to life and that that right cannot be abridged by another individual in just any circumstances (not all killing is murder)

How are these in any way 'pursuant' to the axiom of harm?

Those are subjective claims, Steve.  I happen to agree with both, but they aren't necessary for an objective morality based upon harm. They can, however, both be justified -by- and objective morality based upon harm. You said that you had to ask the question "why"..well, ask it of yourself, for each of those claims. Why do you have value (intrinsic or otherwise)? Why do you have an unalienable right to life (laying aside that it's obviously "alienable" as hyperbole)? Let's try and keep it objective, ghost based answers from magic books need not apply. My chain of why's ends with harm, why is harm immoral - because that's what we're talking about when we talk about morality, harm. No further elaboration can meaningfully add to that answer. There is no and need be no why beneath it. We can comment on how we evolved this or that, but ultimately, we evolved to be and do alot of things - none of which make a lick of difference now in and of themselves. Even if we hadn;t evolved in such a way we could still cogently comment, now, about morality, in this way.