Blaming Clever Sherlock
In retrospect, I’m probably going a little easy on Sherlock.
Did he choose to rattle off a series of painful and embarrassing deductions about Vivian Norbury at exactly the wrong moment? Yes he did. I guess I’m struggling to blame him for that because that’s just what he does. Unfortunately his actions have consequences. But those consequences would have been borne entirely by him and him alone had Mary not thrown herself in their path.
It reminds me of A Study in Pink more than everything else. Sometimes Sherlock risks his own life to prove that he’s clever. John’s presence in his life has softened him a little on that, but it’s never extinguished the tendency. Sherlock is not cautious, and in this case his lack of caution created a dangerous situation with a terrible outcome. So I suppose we can find a way to place a little blame on his shoulders. But he didn’t do anything unexpected.
The bigger miss, I think, is that it took him so long to suspect Vivian Norbury, even while she was sitting right in front of him from the start. He thought she was harmless and horribly underestimated her. That error may have prompted him to humiliate her all the more in the end, which led to her firing that shot.
Even then, I think you have to work pretty hard to blame Sherlock for Mary’s death. He neither pulled the trigger nor aimed the gun at her, literally or figuratively.