First of all, you have a choice to go in or to not go in a store. If smoking is allowed, don't go in. If you go in, then you obviously plan on breathing the air inside. So, if there is smoke in the air (which you should be able to detect unless you are blind and have no sense of smell), then you are choosing to breathe it in. Perhaps a comprise could be a law requiring a sign on the door stating that smoking is allowed.

Besides that, a little bit of smoke isn't gonna hurt you. You'll be alright.