Turned out a bit different from what I had originally planned, but I'm satisfied with it.
Jinchuriki
Mito Uzumaki was not a Jinchuriki as they were thought of in modern times. When she became host to the Kyuubi there was little thought to the action other than that it was necessary. It was necessary to do such to protect the lives of those her husband had taken responsibility of.
It was actually the case with the other Biju as well. The Biju were sealed and dispensed to the other four nations not in order to create some form of weird power balance, but because those nations were the strongest of the time. They were the only ones that could handle the responsibility of managing the Biju.
It was a different era, where the Biju represented not superweapons, but honor in a way. To be the warden of a Biju was to be respected. It was acknowledgement of one's capabilities.
And thus, to be a Jinchuriki of the time was not to be an asset of war, but a symbol of national prestige. Of course, that changed rather quickly.
By the time Kushina came around, sentiments had already changed. Other nations had already begun investigating ways to control the power of the Biju. And so her tenure was different from Mito's, along with her training and seal. Where Mito never touched the chakra of the Kyuubi, not after it was sealed, Kushina was trained to do so from a young age. But it was abstracted, due to her seal. A seal which Mito herself designed.
When Kushina used the chakra of the fox, it was blunted. Filtered even. It was still necessary to grow accustomed to it, but she never faced the full force of it. Of its might. Of its wrath. Of its hatred for all things. When Kushina pulled upon the chakra, she did so through her chains. Suppressing the will and wrath and hatred and all things about it. She essentially left only the energy itself, but in the process, she diluted it and made it lesser. As such, though she could sense everything she suppressed, she never experienced it personally. The greatest side effects she experienced was a significant reduction chakra control and overburdening her chakra system.
Naruto then was a further product of further refinement and understanding of how to deploy Jinchuriki on the battlefield. Although there were distinct differences. The seal applied to him was more a precautionary measure than any planned affair. Created with a specific set of circumstances in mind, something shown in its differences to Kushina's seal. Naruto's seal was built to grant direct access to the chakra of the fox, without any of the filtration done with Kushina's. Naruto's seal was made to intermingle his chakra with the fox from the moment it was sealed within him. Naruto's seal was made recognizing that he would not be able to use the chakra of the Kyuubi like Kushina had.
And it changed him for it. Naruto couldn't control his chakra well not due to his deep reserves, but because it was different. Most people experienced their chakra moving through their body like a river. Sometimes, it might rush. Other times, it would meander gently. People used their hands and feet to control chakra because that was where it was most gentle, most controllable. Far away from the rushing tides of the chest. Naruto's chakra howled through his body. Roaring, clawing, ripping its way through his chakra pathways. It was a turbulent sea, with depths containing fierce currents. Utterly untamable. Only at his hands, far away from the turbulent source does he gain any semblance of control.
Naruto's chakra became a mere facsimile of the force of nature that was the chakra of the Kyuubi. Where Naruto's chakra might've had waves, but the crimson chakra of the Kyuubi was as unrelenting as the tides. It operated on its own, heedless of what its user desired. And how it burned when Naruto used it. The term Jinchuriki was never as accurate before Naruto started to use the power of the Kyuubi. For every time he called upon the power, it burned away at him. His body and his mind destroyed and recreated through sheer malice.
The more he used the power, the more accustomed he became to it, but didn't mean that he ever liked it. For the first few 'tails' of power he pulls, the chakra of the Kyuubi affects him only internally. Subjecting his chakra system to torture and crushing his organs. The reason he goes on all fours is not due to some mental influence acting upon him, but because the pain is ever so slightly relieved when he does so. From the fourth tail onwards, the effects become ever more powerful. His skin rips itself from his body as his blood pollutes the chakra cloak.
And the hatred, oh the seething, festering malice within the chakra that threatens to warp his mind with every breath. Naruto thought that he had known hatred and the effects that it can have from his childhood. What he had known was isolation and loneliness. It was painful, for he truly had seen, had felt what it was like not to be alone when he met with the Third Hokage, but it was only when he first used the chakra of the fox in full that he realized that he had known nothing of hatred. That he realizes that Sasuke, so full of vengeance, does not truly know hatred. All the two of them had known was pain.
How could he, how could Naruto have ever thought that he had known hatred before feeling the bottomless abyss of malice that seemed dwell within every single drop of the Kyuubi's chakra. The pure hatred, the pure malice, the pure contempt for everything that lived and everything that ever will.
It was all that he could to ground himself, to ground his humanity that he look towards, reach towards, and claw himself towards compassion with every fiber of his being. For he did not fear, he knew that should he allow these feelings to seed themselves into his mind, even slightly, that he would truly become the demon that he was feared to be.
So it is not purity, it is not altruism, it is not kindness, benevolence, or chivalry which fuels his compassion, but desperation. It is the desperation of his humanity that drives him towards compassion, for he knows that should he ever pause. Should he ever halt in his endeavors, that he will irrevocably be altered.
Naruto is compassionate not because of an innate nature, but because he is desperate to be human.