I just think the Spurs lost all of their rythym at the half and couldn't get it back in the third quarter. They couldn't find easy buckets, Durant caught fire, and the rest is history. The refs certainly didn't help, but I truly believe the Spurs would have lost even if the game was officiated correctly.
It's easy to get caught up in bad officiating as a fan, because you're always looking for some excuse. But the officials weren't the difference in this series. If you're looking for the difference, try: the wilting of Tony Parker when it mattered most, the disappearance of Danny Green and other role players, an inability to defend the Thunder's best players and an inability to adjust at the defensive end, the complete failure of Tim Duncan to get anything going with his back to the basket, and the continued pussification of Matt Bonner and Tiago Splitter. Or, you can blame the refs. I will admit that blaming the refs feels better.