Doctors are trained to save lives not to be role models, if a doctor is good at his job, his personal life should be of no concern to you, so far as he doesn't smoke while taking diagnosis, if you decide to make their personal live a concern of yours and you can't handle the fact they smoke, change your doctor.

 Back to the question of if doctor's can lie, my personal answer from experience is yes... I'v seen some doctors  add drugs to prescriptions for patients, drugs that they don't need all in a bid to get more money from a patient.