morality is subjective and people don't have free will

[Angrboda]

But I presuppose naturalism without doubting free will.  Given a choice, why would anyone presuppose supernaturalism?  I am fiercely pro natural world, proud to be a natural animal and think everyone with a lofty idea of themselves as a free floating/radically free willing disembodied mind is just off their rocker.

Personally, I find somewhat parochial to maintain a dichotomy between natural and supernatural. Since the distinction is based on what people would consider ordinarily and or possible given what they know at the time. If, as in Newton’s time, someone doesn’t know about nuclear forces the source of the sun’s power would be considered supernatural since no known source of power could keep it burning. Why presuppose supernaturalism? Because every time we think we know all the answers about how the world works something comes along that challenges that paradigm and naturalism gets redefined, as it already has been countless times.

I think you're playing word games. There is the supernatural in the sense of something not being yet explained, and then there is the supernatural in the sense of something that can never be understood naturalistically. You're conflating the former with the latter. Confusing "not understood" with "not understandable". And therein lies the crux of the reason for not presupposing supernaturalism, because most often it is a claim that a phenomena has no naturalistic explanation.

Another reason for not embracing supernaturalism is that you can't explain things with supernaturalism. Steve has given his definition of free will depending upon a mysterious 'Power B'. No matter how much you unfold the rest of his definition, that power B will remain, an unexplained cancerous lump which makes the whole definition useless. Even if supernaturalism were the answer, it would in every case reduce to the explanation "it just happens." Supernaturalism leads to no explanations. If you want to attribute consciousness to a non-physical mind, let that be your starting point. But as we see in things like SteveII's definition of free will, it often becomes the end point of inquiry. If you want to posit the non-physical as an explanation, go out and find me this non-physical. If you just want to use it as a gap filler because you can't get your explanation to work without it, then you're just being useless. A supernatural soul has been postulated for millennia. We're no closer to understanding such a thing for all the talk about it that has transpired.