They don’t lie. Doctors are also humans and have their own weak sides.
Smoking is addiction, that not easy to give up. So, it’s better don’t start.
The Doctor knows that smoking is not good for the health, that's why we are asked to abstain from smoking, because it damages the kidney. But, maybe he is addicted to it. And we knows how difficult it usually is breaking addiction chain. However, everyone do lie, including Doctors, but I think they have reasons for lying.
You should confront your doctor directly. Nothing better than a yelling match in the hospital halls.
Ask him if he was smoking. If he doesn't answer with a clear answer get right up in his face. Don't be afriad to raise your voice and start jabbing him in the chest with your index finger.
Be strong. Show him who is boss.
Shake your head as you leave his office cursing under your breath.
If I doctor smokes, that he/her personal life. Although, I understand that it is not right for a doctor to smoke. Because they serve as role model to others. I think it will be more better asking your doctor in a respectful way why he/she engage in smoking, rather than yelling and creating a scene. Doctor are human too, they have feeling just like us.