After Spock throws a couple of punches at Kirk, Kirk briefly gains his footing and tries counter-attacking, but by doing so, he relinquishes any objectively supported claim to superior emotional stability. In fact, he demonstrates he is less qualified since he is not only now a mutineer, but the basis of his now violent aggression, an actual charge of treason might be plausibly sustained against him as a traitor to Starfleet, instructions from the prime universe Spock notwithstanding.
After about 30 seconds of Spock beating the tar out of Kirk, followed by a silly mockery of choking, note the complete lack of pressure in the screenshot,
Sarek exclaims: "Spock!" After which our skipper moons about the bridge, with Kirk coughing in the background.
Next: Spock "relinquishes" his entire command because of emotional compromise in our next episode of Star Trek by the Minute 092: Kirk Takes Command.