Professionalism is mostly about how you come across to others.
Doctors who smoke, hair stylists with lice, dentists with rotting teeth, car mechanics with no cars that run, none of this inspires confidence in what is your occupation.
The other stigma, is that smoking is highly highly addictive and destructive to society. In some places in the world, injecting heroin is legal. Some people have slammed heroin and not become addicted. Should doctors that can recreationally inject heroin legally, be seen as less professional? Should they refrain from doing so, because of how it might be perceived by the many more numbers of people that are or might be irreversibly harmed by injecting heroin? If they don't, does that inspire more or less confidence in them? From physicians? From heroin addicts? Whose confidence matters most in this case?
This starts to get into, how should we approach the problem of smoking cigarettes? Or injecting heroin?
The reality is that you, as a physician, are arguing for the the right of the few, for nothing much besides it is their right, is pleasurable, and doesn't harm an extremely small minority, over some of the most extreme suffering of millions of humans that we are to ever see in our capacity as healers.
And we're not talking a court room. Of course you have a right to whatever you have a right to in this country. You can argue the above. We're not talking your rights. We are talking about how you are perceived in your capacity as a physician. You don't have a "right" to that.
Most doctors I know go out of their way not to be seen drinking soda in front of their patients. Hypocrisy and rights be damned.
You try to do what's right for your patients. You chose to be seen as their role model.