Starship Polaris said:
Basically, the "Romulans kill Kirk" storyline is disinformation. What actually happens is this: the Romulans do assassinate someone in the past, but it's Christopher Pike. This necessitates Spock contacting himself at an early point in his own career and convincing him somehow to take drastic and possibly mutinous action in order to keep Pike out of a certain (undisclosed) situation at the film's climax.
The SHOCKER is that Spock first realizes that something's gone wrong with time when he encounters his old friend James Kirk - alive nearly a century after he died on the Enterprise B.
So basically Spock has to make the heartwrenching decision to restore history knowing that in order to put things right, Kirk must die.