I think it was the Bowlersparadise.com Classic last year. In the round of 8, Shafer beat Duke 4-3, but the crowd was very clearly on Duke's side. So much so that they were actually heckling Shafer, booing him, trash talking him. I very much doubt Duke encouraged that kind of behaviour, and at the end, Shafer let the crowd have it. It's very bad sportsmanship on the parts of the fans. I can understand rooting for one guy, but actually giving the other guy heck is wrong.
I think bowling Duke has just left a bad taste in Shafer's mouth. Duke's such a fan fave while Shafer seems very cold and off-putting (from TV observation). I thought his little jumping fit when he won a few years ago was kinda corny, and in spite of how well he can bowl, I've never been a big fan.
SH