Reflection proves that we can think about our choices, but it doesn't prove that we ultimately control the causes of those choices. Your brain evaluates reasons using your prior experiences, values, desires, genetics, and circumstances, none of which you originally chose. If those factors determine which option you ultimately select, then saying “I could have chosen differently” only means that you can imagine a different choice, not that you could have actually made it under the exact same conditions. I can still recognize your intentions and treat you with dignity without assuming that those intentions somehow exist outside the causal process that produced them.
if your decision is completely determined by prior causes, then under exactly the same conditions you could not have chosen differently. But if your decision isn't determined by those causes, then what determines which choice you make? If the answer is nothing, that doesn't give you control; it makes the outcome arbitrary. So either the choice follows from causes you didn't ultimately choose, or it happens without sufficient determining reasons. Neither gives us the kind of ultimate authorship required for genuine free will. We can still judge intentions, protect people, and hold people responsible in a practical sense, but that doesn't establish that anyone is the ultimate author of their own choices.