If you think you will be endangered by eating next to a smoker, no law requires you to eat at a place that serves smokers.
You are correct. There is no law requiring me to eat out in a public place.
In fact, back when getting smoking out of restaurants seems far-fetched, I was for restrictions on smoking areas, but still allowing smoking. Common sense things like bathrooms and waiting areas had to be located in the non-smoking section. Smoking sections must be separate rooms or separated by a non-smoking buffer for those people who don't smoke but don't mind.
However, we got an even better resolution with the complete non-smoking ban.
The bottom line to all this is that this is NOT a liberal issue. As I've said, I'm very conservative and this is a non-contradictory conservative position. It is, with no doubt or question, equal to wanting to prevent abortion because it endangers the child. That too is a conservative view. Liberals want to say "if you don't like abortion don't have one" which is, in fact, the argument you are presenting.