Do doctors have the right to just tell patients not to do a certain thing?

They can suggest it, and hopefully provide information on how to avoid doing it.

Smoking is bad; this is hardly news. It slows healing, so smokers have a worse outcome after surgery for example.

Of course the doc should tell smokers to stop.  If the patient wants more info, he should give it.  But lemme tell you that the average smoker knows about as much about smoking as the doctor does.  (most of us don't know that it causes bladder cancer, though)

Of course they "have the right" to tell patients to stop doing things that are harming their health. It's the doctor, not Burger King.

edit: Where do you think you are? Did you think they were going to pat you on the head and validate you? They're doctors! Not Instagram!

You must be pretty young to be asking that question so let me say this....It is one of the most disgusting things a non-smoker can do is to kiss somebody who smokes. It's like licking an ashtray. Totally gross and I almost threw up. No way.

As for does he have the right. Look at it this way you have the right to ignore the advice just like he has the right to kick you out of their office. They don't have to treat you and some doctors tell their smoking patients to find another doctor. Not only does he have the right to tell you but he every doctor out there will or should tell you the same thing. Not only is there a chance of cancer but ending up with COPD tripping over tubes for your oxygen is not something to look forward to. It can make you more susceptible to HPV and throat cancer, heart attacks and everything bad out there. There is absolutely no good in it and yes it can increase your RBC count because it is screwing up your bodies oxygen delivery so he will notice eventually if you continue. 

You went to see a doctor not a plumber or tax preparer or a lawyer or anybody else and if he doesn't have the right to tell you then who does?

It is a doctor's job to tell you what will make your health better.  

Just because a doctor says to stop something doesn't always mean the patient will listen.  

So - Yes - they DO have a right to say things like that.  If you don't like it - try to find a different doctor.  But any doctor that doesn't tell you to stop smoking is probably not a good doctor.  

Doctors can advice what to do and what don't if they are capable of their job. I am not a doctor (fortunately) but I can give the same advice - don't smoke, unless it is a bit of Marihuana every now and than but if your lung is damaged now - stop smoking cigarettes at all right now. If you are upset or nervous, find another way to facelebrate your fears.

Your doctor has A DUTY to tell you how to improve your health.

We may not like what we are told.

We are free to ignore their recommendations 

We can choose to ask for assistance in achieving their recommended actions.

There is unlikely to be a doctor who does not recommend that any of their patients who smoke, stop smoking.

As for the excuse that it "calms you down", scientific studies prove otherwise, what you experience is the relief of withdrawal symptoms. Once you get over the withdrawal, you will actually be calmer without the nicotine in your system, as well as healthier.