How we cite our quotes: All quotations are from Star Trek VI: The Undiscovered Country.
Quote #4
McCOY: Three months before retirement. What a way to finish.
KIRK: We're not finished.
McCOY: Speak for yourself. One day, one night—Kobayashi Maru.
The "Kobayashi Maru" scenario is an infamous test in Starfleet Academy that is literally unwinnable. As legend goes, Kirk beat it by hacking the program. That's top-tier trolling, if you ask us. Context aside, McCoy is grousing about how ironic it is that their future was torn away from them just as it was within their grasp.
Quote #5
KIRK: I was used to hating Klingons. It never even occurred to me to take Gorkon at his word. Spock was right.
Finally, Kirk understands what Gorkon was trying to say all along. Their generation is marred by prejudice and distrust, but future generations don't have to travel down the same path. (Sound a bit like the Cold War generation to you?)
Quote #6
SPOCK: Is it possible that we two, you and I, have grown so old and so inflexible that we have outlived our usefulness? Would that constitute a joke?
His humor might be ehhhh, but his analysis of the situation is spot-on. Spock and Kirk have a great deal of wisdom and experience worth treasuring, but these same qualities also sometimes limit them from appreciating alternate points of view. This is a natural consequence of aging, to some extent.