Why would it kill pubs. People don't got to pubs to smoke. They are talking about licenced beer gardens, not 'outside' as a whole. People can still step beyond that for a smoke just like they step outside the door of the pub.
I get smokers think it is unfair, but I simlarly think it is unfair feeling like I have to avoid being outside, if it is overly smoked up. To some that might not seem unpleasant, to others it is. Lot's of places in europe have smoke free parks, beaches and areas, this would be the same, maybe a smoke free outside zone as someone said. I do think it should be an encouraged choice though, not an enforced rule. To start with at first. Then places would do it based on their popularity and clientele, and punters can choose where to go based on it if they want to.