King Daniel wrote:
Spock has a secret inappropriate relationship with a student, analogous to a closeted homosexual in a relationship
Spock's relationship with Uhura is not secret.
If it was secret he would not be worried about appearing to practise favoritism by assigning her to the Enterprise. It would just be an instructor giving the best student the best assignment, to everyone's eyes.
And since it's not a secret and none of them has any consequences that we can see on their career, I assume it's not considered inappropriate either.