I do understand what you're saying. The problem is that in order for us to accept your derivation of "Absolute Behavioral Maxims," we must first accept a huge pile of a priori assumptions and pre-conditions. There's no point in accepting your reasoning if we don't agree on the terms under which your reasoning is conducted.
In your mountain climbing example, you've arbitrarily disallowed any other means of reaching the top of the mountain. IF there are no other means, and IF I want to get to the top, THEN I have to climb. Of Course it's an absolute behavioral maxim in that case, but so what? In defining your conditions, you've dodged the Objective Fact that there are still many other methods for me to reach the top. Your behavioral maxim is therefore not "absolute" in the real sense of the term. It's only "absolute" within the arbitrary constraints you've placed on the problem. You've merely assumed away the underlying "moral problem," which is to decide which among of the many available solutions are truly available to us.
In the same way, you've explicitly disallowed Mr. OWK from undertaking any other actions to keep from being murdered. It's a stacked deck that pretty much demands your conclusion: And at the point that the Atheist Mr. OWK deduces by enlightened self-interest as a matter of Objective Fact the Reflexive Necessity of contracting an Absolute Social Compact in order to accomplish his Objective of Not Being Murdered.
The reasoning leading to this conclusion is simply wrong, on several counts.
First, you arrived at this conclusion by a priori assuming that none of the other existing options were acceptable. You've provided no justification for this.
Second, when we acknowledge the availability of other options, it is quite clearly not an Objective Fact that Mr. OWK must, of reflexive necessity, join this Absolute Social Compact. Rather, he may simply choose to join this compact -- or to choose some other approach. He's not required to join at all, unless there's a real and absolute reason for him to reject all other options.
This is where God comes in. As the Rabbi pointed out, only God can exclude those other alternatives. (And, of course, the alternative that God allows is not the one that informs Mr. OWK's maxims....)
Without God, the only basis for choosing for or against the options is what we can observe and derive from observation. Mr. OWK's "absolute behavioral maxim" is observably not the only viable alternative -- and in those circumstances, a moral system that claims to derive the "Absolute Behavioral Maxims" you derived, is quite simply fraudulent. (Ayn Rand's philosophy is fraudulent for precisely this reason.)
No, you are still presuming that an Absolute Behavioral Maxim depends upon Necessity of Exclusivity. I already told you that it doesn't. It depends upon Necessity of Consistency (i.e., whether or not adherence to the Maxim must be absolute in order to accomplish the Objective).
I already told you that I was skeptical as to the value of my Time if you couldn't grasp that point. It's pretty explicit in my Writings thus far, and I (quite reasonably, IMHO) asked you to re-read them with a little more attention to detail.
But I'm feeling charitable. I will give it one more shot. The "absolute" quality of a Fact-derived Behavioral Maxim does not depend upon the Necessity of Exclusivity, but upon the Necessity of Consistency. Look, I'll illustrate -- Here goes.
Now assume that there are two wide, easy, clearly-marked paths to the top of the Mountain, each measuring 1000 paces exactly -- one from the North face, and one from the South face.
Now, we'll allow each of our Free Agents to choose their starting point, whether from the base of the North face or the base of the South face (call their starting points their "assumed basic premises", or some such). For the sake of the example, we'll assume that one (Mr.A) chooses the North base and the other (Mr.B) chooses the South base.
Now, at this point, we have established that there are two entirely different Paths to the Top of the Mountain -- as objectively different as proceeding south is an objectively different behavior than proceeding north.
And yet, in either case, our Free Agents in question must absolutely adhere to their chosen Path if they want to reach the Top of the Mountain.
Thus we see that the "absoluteness" of a Behavioral Maxim does not depend upon the Necessity of Exclusivity, but upon the Necessity of Consistency. There are two entirely different Paths to the Top of the Mountain (i.e., not an Exclusively-mandatory course of action); but whether he proceeds from the North base or the South base, the Free Agent in question deduces as a matter of Objective Fact that he must adhere with ABSOLUTE Consistency to the appropriate Behavioral Maxim for reaching the Top of the Mountain.
And in either case, there is not necessarily any transcendent moral value assigned to reaching the Top of the Mountain -- it is simply the desired objective of the Free Agent. And there are two entirely-different starting points and two entirely-different Paths which our Free Agent may choose. But once he selects his starting point, he rationally deduces that he must adhere with ABSOLUTE Consistency to the appropriate Behavioral Maxim for reaching the Top of the Mountain.
As I said -- Thus we see that the "absoluteness" of a Behavioral Maxim does not depend upon the Necessity of Exclusivity, but upon the Necessity of Consistency.
Does that make sense yet, or (meaning no offense) should I just throw up my hands and despair of your understanding the point?