The Slippery Slope Argument for a Smoking Ban

Study after study has shown that restrictions on smoking in restaurants and bars actually leads to more business, not less. Those banning smoking indoors now have been in existence for about 30 plus years. How can you tell if a slippery slope argument is valid when you're standing at the top of the slope? The questions we have too, raised here, are will a lead to b, will b lead to c, and then is the undesirable? Is there no way to stop the slope, as it were, stop on the slope and go back?