I'm very unclear on your question, and where you think the contradiction lies. Being addicted to a drug that you will reliably seek despite considering it wrong would reduce your "free will," as it would take you closer to being "never uncertain of my future decisions, or in a brain-state where my emotions and morals fail to determine my actions in the usual way."

(I would personally not have included the "uncertain" part before encountering Eliezer's work, but of course other writers do treat it as important.)