Joining Star Fleet was the reason for tension between Spock and his father. Something that never got totally resolved. Surak spoke of it to Picard and then did the mind meld shortly before dying.
Maybe it just that one Vulcan family that felt that way about Star Fleet?
It’s always seemed much more a case of being annoyed at Spock ‘squandering’ his potential. He had potential to go far in the Vulcan Science Academy, but he gave that up to become a Starfleet officer, limiting his ability to live up to the potential Sarek saw in him. He might get to research some novel things out on the edge of the universe, but he’d always necessarily be a Starfleet officer first, a scientist second - and a Starfleet scientist, not a Science Academy scientist to boot.
Just wanted to pop in and say that this episode, back when it was first on TV, was the very first episode of Star Trek I ever saw. I was in sixth grade, 1966-7, and I thought the show was the greatest thing I’d ever seen. I fell completely dropped my first love, Lost in Space, when I saw how much more mature this series was.
I thought it was because Sarek was a committed pacifist, and objected to Spock joining a military organisation.
Alright, we’ve had some fun with this one, but I think it’s time to shut it down.
It was both reasons. Sarek thought Spock had more potential and he objected to Star Fleets military function.
I’ve been trying to recall in TOS if Spock ever killed anyone. He phasered a bunch of folks, but it was on stun. Been too long since I watched to say for sure.
He killed kirk - twice.
Maybe not in direct hand to hand combat, but he was a participant in space battles in Balance Of terror, and Wrath Of Khan. The enemy was destroyed in part because of Spock’s actions. I personally would count that as killing, other people might disagree.
(Referring to the ship that got blown up with the all Vulcan crew.)
Well, IIRC, it was mentioned somewhere that Starfleet ships usually had all-human or all-Vulcan crews, never mixed, with Spock being the exception to that rule aboard the Enterprise. So the Vulcan ship was Starfleet too? I don’t think it got blown up. It got more like eaten by a life-energy sucking space blob, IIRC.
You RC - it was “The Immunity Syndrome”.
@Baker: I well remember the first Trek clip I ever saw, which was from “Arena” - the part where Kirk drops a rockslide on the Gorn. My reaction, when I first saw an episode, was much the same (didn’t watch Lost in Space, it was Doctor Who that I was initially resentful at being displaced by this American import).
My personal (admittedly unexciting) guess: since this was a first season episode, this was simply a concept or a plot germ that was abandoned/forgotten as the series’ “universe” shaped up. You see plenty of inconsistencies like this in early installments of anything—heck, like the “United Earth Space Probe Agency” mentioned occasionally in TOS, or Data saying he graduated in the “Class of '78” (in an episode taking place in the 2360s, and he’s not over a century old) in TNG.
Early on he certainly advocated killing people and life forms with no hesitation: the officer turned egomaniac being with kinetic powers in “Where No Man has Gone” and the Salt Monster
in “The Man Trap”.
I always thought he was more logical then. I never have understood why the society that was supposed to be so intensely logical would have such an intense concept of right and wrong. You’d expect them to be more utilitarian.
But that’s nothing compared with making them so inundated with ritual. Eventually you just had to accept that the idea that they were pure logic was just lie they tell themselves. It’s why later series came up with the idea that all Vulcans (and not just half-Human Spock) were just burying their emotions.
As for the idea about Vulcan traitors: I’d assumed it was a common epithet due to the original concept. If you do do everything by pure logic, you’re going to do a lot of things that would be judged as traitorous, as loyalty is not based on logic.
By Spock’s own admission, given the right circumstance for it Vulcans, even Sarek, can kill efficiently.
Part of the potential germ of truth in Kirk’s insult lies in that we know that a lot of the Vulcans’ all-logic-no-emotions “enlightened philosophers” act is just that, an act they’re paternalistically pulling on the other species, not having themselves really achieved it to the extend they pretend.
(BTW the reboot movie also includes a sequence in which Kirk provokes Spock to violence through insults upon his family in order to disturb his mental state. And that he ditched the VSA for Starfleet after being condescended to as some sort of affirmative-action admit)
Well, our crew has some particular sensibilities…
This is probably closest to what ended up as canon. Remember that 1960s writers weren’t planning on a 50 yr run.
In later eps, movies, and series, we see glimpses of how this could ring true(ish) to Spock’s pointy ears. We see him him leaving Vulcan to join Starfleet against his father’s wishes. We see him failing at Kolinar. We see him showing emotions. We see him lying. We see him using subterfuge for his own ideas (reunification with Romulus).
So, in hindsight, it could’ve bit him at his very core. The “race” part was simply Kirk using hyperbole.
But the main thing is, it was 1960s TV show writing. It just needed to be a good sound bite.
My first one, at about the same age, was The Empath. Had a similar reaction, too.
I’m glad you made me look at that up, as I would never have guessed it was from the 3rd season.
Back to the OP - Kirk knew he had to be extreme to raise emotions in Spock. One of Spock’s most important characteristics was loyalty - remember he risked the death penalty to get Pike back to Talos IV. Calling Spock - and Vulcan in general - a traitor was as far as he could go, and it worked, after all. So I don’t see any history of disloyalty implied here.
I guess I read to much into the insults. They only have to get through Spock’s logical discipline.
If the shoe was on the other foot, and Spock was complaining about how Humans were a bunch of thieves, it may not be true, but it might do the job.
Then again, maybe not. 
Spock is always remarking on how humans were undisciplined, irrational, etc, etc, and needed his guiding hand, yet Kirk rarely growls at him. (Mirror Mirror quote: “…brutal, unprincipled, uncivilized, treacherous; in every way splendid examples of Homo sapiens, the very flower of Humanity.”)
I think that’s generally correct, but I also see a slight nuance.
Spock keeps his cool during the accusations about his (and Vulcans’) integrity. It’s not until Kirk starts hitting the circus freak buttons that Spock gets annoyed; he loses it after Kirk says he belongs on display next to the dog-faced boy. The odd thing about that is that Kirk knows Spock very well, and he knows what buttons to push – so why hold that one till last?
It may have just been tactics, of course: building up to the big insult. But I like to think that Kirk was hoping not to have to go there. The first insults were abstractions about Vulcans; the later and more effective ones were at Spock individually, and came from knowledge Kirk had gleaned from their friendship. I can see Kirk hesitating to use such knowledge.
Except that he leads off with “half-breed”, which is directed at Spock personally. And which ties in with the circus freak business.