The Wormhole wrote:
But the truth is, the crew broke the Prime Directive the moment they decided to screw around with the volcano at all.
And Kirk got chewed out and demoted because of it. Seems pretty consistent with canon to me.
As for Spock's attitude, in TOS Spock didn't follow a strict and rigid definition of the Prime Directive, and showed a willingness to bend it on occasion, or at least go along with Kirk when he chose to interpret the Directive his way. Obviously saving the tribe from a volcano is deemed an acceptable bending to Spock, provided it can be done without the natives being aware of it.
This. Spock didn't have any qualms with it as long as no one got caught. When the jig was up, he was willing to die rather than have the Enterprise revealed to the natives in an effort to save him.
The thing I don't think has been discussed in all this time (or I've forgotten if it has) is what Spock would've entered into his log if things had happened as planned. Would he (and Kirk) have gotten into trouble with Starfleet if Spock reported that they detonated a cold fusion device in a volcano about to destroy a planet with intelligent life, but they never revealed themselves to the natives?
Did they get in trouble for what they did, or what went wrong with what they were trying to do that led to the natives seeing the Enterprise?