@Briancrc,
Why behaviors come about is a complex issue, too complex to be left to behaviorists. But you agree that the mental life is just as real as anything else, then no reason to dismiss emotions and feelings and ideas from the equation. They play a role, in my view a crucial role, or they would not exist.
Descartes concluded that God could not lie to him that much, and thus could not have placed him in an illusionary world. Therefore the world must exist. I use a similar argument where evolution replaces God: over the long run, evolution creates and maintains useful organs and functions, and only those (vestigial organs notwithstanding). Thus it could not have lied to us that much to create a purely illusionary sense of agency.
Because such an illusion would be useless for survival.
You argue that such a free will illusion is
damaging for our well-being, our societies and our survival. But then, how could such a damaging trait have been selected by evolution????
Nature can't lie that much.