Sherlock is counting on John to believe the worst in him. And John does. For the entire episode up until that point, John has been fighting Sherlock’s corner and defending him no matter what while others have fallen for Moriarty’s plan. And while Sherlock is at first indifferent as to whether people think he is a fraud or not, the one time he does care and starts to panic about it is when he thinks John is beginning to doubt him. It’s a double tearjerker; firstly for the fact that John’s belief in him means so much to Sherlock and then he has to purposely shatter it to save his friend. And secondly; the fact that it worked and John did lose faith in him. It was only for a moment but it was enough for him to turn on Sherlock and leave him all alone to his fate.
For extra heartbreak, what does John says this at Sherlock’s grave, “ Um, you once told me that you weren’t a hero. There were times when I didn’t even think you were human, but let me tell you this- you were the best man, the most human… human being… that I’ve ever known and nobody will ever convince me that you told me a lie.”
John pointing out that he knew Sherlock was the “most human… human being…” functions as an apology because one of the last things he ever did was call Sherlock a machine. It may also be a reference to the fact that John had once made the mistake of calling Sherlock ‘Spock’ when he was in the middle of having a panic attack. John never got a chance to tell Sherlock to his face that he didn’t mean those things. And while we all know Sherlock is alive, John thinks he will neverhave a chance to tell Sherlock he was sorry, and probably thinks calling Sherlock a “machine” and turning on him about Mrs Hudson may have been a catalyst in hissuicide.
On the above, this is John’s current, end-of-season-2 view of events: he was called away to Mrs Hudson. Sherlock coldly refused to go with him. They had an argument which more or less involved John yelling at Sherlock, who was uncharacteristically passive, who couldn’t even force himself to look at John; even more: he was avaiding John’s eyes. Yet John abandoned Sherlock in the lab. He found Mrs Hudson and she was fine. He rushed back to St Bart’s in time to witness Sherlock’s suicide from the roof.Sherlock had shown no signs of being suicidal before. None. The last time he and John talk before the “Mrs Hudson” diversion, Sherlock’s messaged John because he’s apparently had an idea about using the code against Moriarty. It’s nonsense, of course, but to John it’s pretty clear that Sherlock intends to beat Moriarty, and people intent on committing suicide don’t plan for the future like that. The rooftop jump, so far as John would be concerned, would have come out of nowhere. John seems to not know that Moriarty was ever on that roof with Sherlock. The only suicide trigger that would be immediately obvious to him? His turning on Sherlock and abandoning him. Yep, that’s right. There’s no sign that John ever believed Sherlock to be a fraud or a kidnapper, but he was Sherlock’s best friend, and on the lam, his only friend. And when Sherlock was in a dark place emotionally, he made the mistake of criticizing and then leaving him. No wonder he’s in therapy. He blames himself.
And when John sounds like he’s choking back a sob and says, “Probably one the the killers that you managed to attract! Oh Jesus!”
On top of calling him a ‘machine’ and abandoning him, John essentially says that it’s Sherlock’s fault that their landlady is dying. Having that sort of guilt on your shoulders on top of the rest of your life falling apart most likely would drive someone to suicide. John can’t be certain whether the thing was set-up by Sherlock or an outside party but the accusation, which even he finds too harsh and has to cut himself off, was still heart-wrenchingly brutal and would add to the list of words that would no doubt haunt John until he discovers the truth.
