Jon, I agree with all you've said.  The score is incredible, dramatic and intense!  Just what was needed.

Yes, Spock uses that line after Decker claims that he's bluffing.  Spock says the line and calls over two security guards. That crew isn't following anybody from another ship no matter his rank!  It only gets to that point after they establish communication with Kirk.  Before that, Spock resists Decker, but backs down when rules are quoted to him, despite Bones wanting Spock to mutiny--a great scene, by the way!  The whole thing is.  Once Kirk orders Spock to take command, ain't no one backing him down.  I love those little bits in the series (and occasionally in the films). 

There are quite a few excellent episodes from the second season, but I'd have to say this one is my favorite of them all.