Answer

Where exactly am I not addressing it? I’ve written books and articles about these very things, so if you would be so glad to hear my response, it is at your disposal. See my books The Science of Freedom and Man Is as the Grass, and the articles here on the site about freedom of the will. In general, every justification begins with first principles (axioms), and therefore there cannot be a justification for the first principles themselves. Does that make them arbitrary? Obviously not. On the contrary, they are true in a self-evident way and therefore do not require justification.
See the article I wrote explaining that Leibowitz did not understand himself on this point about the arbitrariness of the will. This too is another place where I supposedly “didn’t address” the point you’d so much like to hear my response to.