Forgive me for going a little OT here on my first post but when I read this I had to address it.
"It's not surprising they had to bend the rules a little. They were a little slower to invoke the Prime Directive and a little quicker to pull their phasers. Of course, the whole bunch of them would be booted out of Starfleet today."
I never liked that comment by Janeway as I felt that it showed how little she knew about Kirk and Co.
Kirk's primary concern was upholding the spirit of the Prime Directive over the literal Letter on the page.
Example: A Private Little War. For all intents and purposes the Prime Directive didn't apply anymore because the Klingons (who were not under any such constraint) had already started interfering in the normal developments of the planet and it's inhabitants. if anything, Kirk, despite McCoy's misgivings, was trying to restore the planet's normal development.
Many of the other instances of "violating the PD" are similar. Either, the Prime Directive was already Violated by an outside party or the Planet had been tainted prior to the Prime Directive going into full effect. (i.e.: "A Piece of the Action")