He didn’t answer because he knew they didn’t have to fight. They were fully immunized and could beat a hasty retreat to the *Enterprise *any time they wanted to.
But it doesn’t violate the Prime Directive to interfere with an advanced culture - otherwise, fighting with Klingons would be a violation of the Prime Directive. One version of the Prime Directive (it seems to take different forms) says that even revealing the existence of the Federation is a violation of the Prime Directive - so either the whole Federation is violating the PD by ordering Kirk to take an ambassador to the planet, or the Federation thinks that the PD doesn’t apply to this planet (now there may be another rule about meddling in the politics of another advanced civilization - but that rule isn’t the PD).
Interference is interference, regardless of how developed a culture is. It may have been done in self defense, but Kirk is upsetting a situation that’s endured for hundreds of years, and neither of the two warring cultures will ever be the same again.
Neither was he setting right a situation for which the Federation was responsible, nor was the Federation at or threatened by war. The only justification for interfering in this case is that he was protecting his ship.
I’m open to the argument that it’s wrong to interfere with a culture, no matter how advanced it is, but not convinced that the Prime Directive says anything about interfering with an advanced culture. And as I said, if the Federation doesn’t want to risk interfering with Eminiar VII, the way to do that is to not order a ship to go there.
The Prime Directive supposedly forbids interfering in the normal social evolution of a planet. In pre-warp cultures, this means you cannot even hint at the existence of other worlds. I submit, however, that stopping a war which has formed the basis of two advanced societies for hundred of years is interfering in their normal social evolution as well.
The *Enterprise *was sent to Emeniar VII to open diplomatic relations with it, since it was already known it had a highly advanced culture. It was not known at the time that it was at war with Vendikar, and had been for hundreds of years. Even if it was, that would not have provided grounds for interfering in their normal social development. The Emeniarans were free to accept or reject the offer of diplomatic relations as they wished.
It occurs to me that for a long time I thought Tracey was a little nuts in his assessment of the value of a Fountain of Youth and how the Federation would react…then Insurrection came along and he was right the whole time.