How we cite our quotes: All quotations are from Star Trek: The Motion Picture.
Quote #7
McCOY: It's an obsession—an obsession that can blind you to far more immediate and critical responsibilities. Your reaction to Decker is an example.
This exchange makes us think about Captain Kirk as Captain Ahab, which is a metaphor the Star Trek series later employs to great effect in First Contact. In many ways, the Enterprise is Kirk's Moby Dick: an all-consuming obsession that threatens his own life, as well as everyone's around him.
Quote #8
McCOY: Well, however it's pronounced, Mister Spock, it's the Vulcan ritual supposed to purge all remaining emotions.
KIRK: The Kolinahr is also the discipline you broke to join us.
It's worth noting that Spock is actively neglecting his duty as a good Vulcan by taking part in this mission. Not only is he abandoning the Kolinahr ritual before attaining the blissful state of pure logic, but he's now actively embracing his human side and all of its emotional messiness. For (the human emotion of) shame.
Quote #9
DECKER: We don't know it will do. Moving into that cloud at this time is an unwarranted gamble.
KIRK: How do you define "unwarranted?"
This is a nice encapsulation of the difference between Kirk and Decker. Kirk is your classic old school adventurer: he acts first and considers the consequences later. Decker, on the other hand, prefers to weigh and analyze each decision before taking action.