He wanted Spock to be happy above all else and if helping Vulcans to reestablish the species was the way to make Spock happy then it was wrong of Jim to do anything to prevent that.
It was up to him as both Spock’s friend and commanding officer to ensure that Spock’s needs in that regard took priority over Jim’s own personal needs.
He erased what he typed out and re-typed out,
We need to talk. My quarters at your convenience.
This time he did hit send.
And now the only thing he could do was to wait.