But that decision was about ECB's QE, I don't think this is as clear as you make it sound. SNB could have chosen to continue the peg through any ECB actions, but instead they chose to scrap it. It was still their decision, although you can argue that they wouldn't have been successful had they decided to continue the peg.
I may be wrong, but I think the decision to get rid of the cap was ultimately the result of an ECJ's judge statement made the previous day: http://www.telegraph.co.uk/finance/economics/11344253/ECJ-ru... , so not much that SNB could do about it.