(SPOILER)My reading of the episode is consistent with Psy/Del's, and it seems to be what the finale was most straight-forwardly hinting at: that Hurt is the Doctor incarnation from during the Time War, and he's the one that sealed off "all" of the Time Lords, Daleks, etc. The Doctor has never been particularly proud of his conduct during the Time War, so it would make sense that he would refuse to recognize the part of himself that existed at the time.