Pretty sure he had no real interest in marrying T'Pring, but he gets in a parting shot
He just wanted to get back to the ship and face what ever consequences Starfleet had for him.
You have to admit, for a "logical" people the Vulcan's traditions lead them to pretty absurd situations! Just imagine! If Kirk had died, Spock in spite of seeing through T'Pring's plan gave her exactly what she wanted, rewarding her villainy, he killed his captain and ruined his life. And all that because of those idiotic customs of an allegedly logical people!
