It is ridiculous to blame one person for another person's decision to commit a crime, just because they allowed that person to end up in the position to commit that crime. That's like saying that the co-worker who let Lee Harvey Oswald
use the elevator in the Book Depository on November 22, 1963 was to blame for JFK's death. Or that it was the fault of the other co-worker who gave Oswald a lift into Dallas that morning, or the boss who hired him for the job at the Depository the previous month. If you use that kind of indirect logic, you might as well blame everyone who ever fed him or clothed him or did anything that sustained his life or activities in any way. It's nonsensical. The person who is responsible for a crime is the person who decides to commit it.
The only way you can hold anyone else responsible is if they knew
the crime was going to be committed and did nothing to stop it. As I've already explained, Kirk could not possibly have known that Khan would commit an act of violence on such a scale, because even Khan did not know he was going to do that
. It was not his plan from the start; it was simply the only option left to him after his real plans were defeated.
Sure, people would probably blame Kirk based on the kind of reasoning I'm hearing, but it's emotional and irrational reasoning, not something that would remotely hold up in a court of law or a disciplinary hearing. Kirk acted entirely appropriately, in proportion to the level of the threat as he was aware of it at the time
. As I said, Starfleet rules of engagement would make it illegal to use lethal force against someone before
you had any reason to believe such force was necessary.