The problem with the 50th ret-conning isn’t that the Doctor’s emotional integrity re: his post-Time War angst disappears. Obviously, he really believes he sacrificed Gallifrey, believes all those people burned, etc. He’ll still feel really, really bad about it.
The problems are that:
A) OUR response as the audience to the first seven seasons of NuWho has been compromised because WE know that it’s all a lie. The emotional resonance of those scenes is irrevocably altered because instead of feeling the weight of that choice and empathizing with and/or shuddering at the Doctor’s actions, we become sympathetic — the poor dear just doesn’t know the truth. Don’t worry, though, he’ll find out in time that it was all a lie, the wee lamb.
B) It has fundamentally changed the nature of the Doctor’s character. Before he was actually capable of causing that much destruction. Now he is not. That detracts hugely from the character because it erases one of his flaws — that in the right (wrong) circumstances, the Doctor could be terrible, fearsome; he has the capacity for that inside him. That he chooses to be otherwise, as much as he is able, is what makes him heroic.
Think about the conversation in Boom Town between the Doctor and Margaret the Slitheen. He has her number, absolutely understands her motivation, calls her on all her bullshit, and what does she say? ”Only a killer would know that.” The truth of that moment was brilliant, powerful, and a little disturbing — we are meant to fear him a little because of it. Now we know we don’t need to, we never need to, because the Doctor?
Oh, he’d never do a thing like that.
….I find myself with a bit of money and considering the Christmas self-gift of pair of antler hair clips…
So…has anyone ever made a sonic screwdriver that was actually a screwdriver?