In regards to Dr M'Benga killing the diplomat?
I supposed this is two questions, whether a federation doctor should have been written to have killed a person as well as how Captain Pike / Starfleet should handle it in Season 3.
There is no spoiler protection here for episode that aired more than a week ago, let alone...
checks notes
nearly four months ago.
I see references of previous Starfleet officers such as Worf or Captain Sysco;
With Worf the writers where careful to create a scenario where it was known and out in the open, that the only Federation law he broke was leaving the ship without authority, which he was officially reprimanded over. The actions he took on the Klingon vessel were considered lawful in and of itself.
Captain Sysco's may be more relevant and example, but to me it felt more like a necessary decision for the benefit of future outcomes. To compare this to SNW S02E08, I don't feel they outlined that he was a future threat to anyone, that being said I am undecided on the Sysco comparison.
I have also seen reference to Captain Picard's assimilation, but to me that one is not appropriate as it was against his will.