You have received answers from various perspectives which can be helpful to round out your own.
I have a challenge to answer with neutrality, as my feelings are strong about smoking. I would not suggest to a person that they stop smoking (unless invited.)
But, I am so highly sensitive and allergic to cigarette smoke my reply will be charged with a feistier energy than usual. We moved to Germany in July, and were shocked to see how many people smoke. On every corner.
In public eating areas, the law forbids smoking. But people gather right outside the door and puff.
So when we are in a bakery enjoying a coffee and brotchen, and people start puffing, we both get scratching in our throats, our sinuses swell, we have headaches, and our pleasant time out is in ruins.
I have seen so much rudeness from cigarette smokers, it rounds out my perspective to look at it from a smoker's viewpoint.
On the beaches here, cigarette butts are thrown on the sand. Do the smokers ever consider that others might not want to see their butts on the ground, or that it can be harmful to nature?
From a legalistic viewpoint, if you are in a smoking permitted area, you have every legal right to smoke. And I would say it is outside the bounds of proper social behavior for a non-smoker to expect you to stop smoking.
As others have suggested, if the tone was friendly and made as a request, it was not rude. No more than asking, "Excuse me, would you please move your shopping cart so I can pass?" Shouldn't humans be able to make such requests of each other, without expectation? If they had expectation, I would say it was rude, or uninformed about the smoking permitted status.
Then I wonder about your reaction. You probably just wanted to be left alone to smoke. Perhaps you felt guilty about smoking, after the request? If you can smoke and not care how it affects others as long as you are legally within your rights, why should it matter if someone asks you to not smoke where they will smell it? I mean, you don't care about them so couldn't you let the comment pass over you and remain confident with your smoke?
There is the point that you sat far away from everyone else and the non-smoker sat next to you. If they had a choice to sit far enough away to not be affected, well, if it had been me, I would have moved and said nothing.
Also, if you had pointed out to me that you are sitting in a smoking permitted area, and I had asked you to not smoke, then I would apologize.