Yeah, Jack would never understand all that. He feels like he's true to himself (and to the Doctor's legacy) in his actions, but as for his persona, the way he presents himself, almost everything is deliberately put on, or at the very least a deliberate exaggeration of qualities he already possesses) and he can't understand why someone would moan about not being liked or respected and not do something to fix that.
As for the conversation they're actually having out loud...
"What? That's not what I said! That's not what I said at all!" More incredulity. "Of course life has meaning. It has the meaning you give it. Isn't that why we risk our lives every day to save others, to make the world a better place?"