He’s trying to show some passion but it just comes off as petulance.
I agree. This wasn't even close to a "meltdown." This was supposed to be Jeb, "enraged?" Hardly. More like a joyful (yet disruptive!) tortoise flailing on its back trying to simulate what he imagines might sound presidential. It was moment calculated by a team of worthless consultants, which combined with Jeb's flaccid personality, failed miserably.
They were going for passionate, presidential and principled and the only P Jeb manages to squeeze out is petulance.