Yes, medical science has no normative force. The fact smoking leads to cancer is a claim about causal relationship between phenomena in the physical world. The fact cancer causes suffering and death is also such a relationship. The idea that suffering and death are evil is already a subjective preference (subjective not in the sense that it is undefined but in the sense that different people might have different preferences; almost all people prefer avoiding suffering and death but other preferences might have more variance).
Yes, medical science has no normative force. The fact smoking leads to cancer is a claim about causal relationship between phenomena in the physical world. The fact cancer causes suffering and death is also such a relationship. The idea that suffering and death are evil is already a subjective preference (subjective not in the sense that it is undefined but in the sense that different people might have different preferences; almost all people prefer avoiding suffering and death but other preferences might have more variance).