The thing about Kim Kitsuragi is that yes, he is a deadpan straight man to Harry's eccentricity, but it's very clear that he's not oblivious -- just gifted with an infinite capacity for forgiveness and unconditional support. Which is why it hurts so much to disappoint him.
I think it's crucial, from a design and storytelling perspective, that Kim is specifically capable of being disappointed but also not guaranteed to be. He is legitimately judging your actions and choices, but he also shows up willing to give you the benefit of the doubt—he's heard of the 41st and he's heard of you, so he's inclined to believe that there's method to your madness. He's not a cartoon character who will always react with disparagement or unconditionally support your craziest rambles.
And because he's willing to judge Harry's actions by their intent and outcome rather than their method, he ends up effectively judging the player themself—who is only able to express their intent through Harry's deranged methodology. So when the achievement pops up and you learn that Kim truly trusts you, you as a player feel seen and validated in a way that video games seldom achieve.
It's also important that he is written as a whole person, with his own idiosyncracies and interests and pet peeves. He's not a paragon of virtue and moral good to measure yourself against.
For example, he will not approve of your interest in pinball machines, disapprove of any attempt at playing with them or bringing them up. He will dislike you pushing him on this... Purely for personal reasons. He had a previous experience with them that he does not want to revisit, and he hates pinball as a result. But pinball is not morally wrong. You're not a bad person for liking it, obviously.
His politics are also his own and the game is clearly not holding them up as the "correct" politics to have. He will most likely disagree with you politically, but is willing to hear your perspective and maybe even come to respect it.
Unless you choose fascism, in which case he will absolutely not hear your shit because you will be rightly irredeemable in his eyes
Which is why doing a fascism playthrough is so painful and I've never finished it.