If you believe Slush's explanation, which I do, then it is seems inappropriate to refer to this situation a "block withholding attack".  A better term would be "block withholding bug". 

As to people who believe that Slush "owes" them something.  We all had access to the same information and had the opportunity to move our hash power months ago, once it was clear that something was wrong.  I stopped mining at the pool some months ago, once it was obvious that the bad "luck" was almost certainly not luck.