Kakashi mishandled things with the hospital disaster, and he only continues to worsen things with Sasuke in his treetop chat. Kakashi bungles this pivotal conversation, making this scene an important moment contributing to Sasuke's fall. It also captures how incongruent Kakashi's and Sasuke's perspectives on life are, as well as highlighting how Kakashi and Sasuke diverge in how they process trauma and suffering.

Firstly: a pupil will either listen to his teacher, or he won't. A teacher can chatter away at a student all he wants or tie them to a chair and force them to hear his words (which is essentially what Kakashi does here), but you can't force a person to LISTEN to you – by which I mean you can never force a person to critically and thoughtfully process what you saying. Nor can you force them to absorb the knowledge a teacher has imparted on them and additionally take action to implement these teachings into their own life. That interest in chewing over information can never be forced. Anyone can talk at anyone, but it's getting the hearing party to actually listen and be willing to listen that is the real challenge. People won't listen to virtually anything unless they decided beforehand that they want to. They choose when they want to listen, on their own terms. Otherwise anything you say to them will be met only with defensiveness, hostility, and objection after objection, no matter how flimsy or silly the objection might be.

Tying up your student to force them to listen to your advice is wrong and ultimately pointless. Kakashi needed to use other methods to make his words compelling or of interest to Sasuke, whether that be waiting until Sasuke is in a better mood or threatening suspension from the team if Sasuke refused to listen. But tying Sasuke up like a criminal sends a lot of bad messages, it doesn't help anything, nor is it conducive to making Sasuke a cooperative or engaged audience.

If Sasuke doesn't respect Kakashi enough to even spare a couple minutes to hear his sensei out, then Sasuke isn't going to respect anything Kakashi has to say, period. People don't listen to people they don't respect, they only listen to people that they do respect or at least are willing to hear out. Respect isn't commanded, it's earned.

Kakashi has done such a terrible job as squad leader that even his subordinates are done with him and don't want to follow his lead anymore...

...at least that would be true on the hypothetical assumption that if left free, Sasuke would take off, shove his fingers in his ears while obnoxiously humming to block out any of Kakashi's words the second his sensei tried to instigate a conversation.

But we don't know for a fact that Sasuke would have refused to listen to Kakashi. Kakashi just assumed Sasuke would take off, and that's not even a great assumption. Maybe Sasuke would take one look at Kakashi and run away, but more likely Sasuke would sit and hear Kakashi's advice, no matter how reluctant or hostile he appeared to be towards hearing such advice. Even if he was annoyed at Kakashi, had Kakashi given him the option, I'm sure that Sasuke would hear out anything Kakashi had to say, even if he was disinterested in what Kakashi had to say. But that doesn't change anything, since Sasuke wasn't interested in being lectured by Kakashi when he was tied up either.

Sasuke made it clear he was hostile to his teacher's lecture. It's not like Kakashi's wire was a magical rope that transformed Sasuke into a suddenly compliant student inspired by his gray-haired sensei and admiringly look up to Kakashi for any tidbit of wisdom he might be selfless enough to toss down to his pathetic Uchiha pupil. That's not what happened.

Instead, Sasuke glares fiercely upwards at his teacher in fury. 

Problem is that right from the start Kakashi doesn't even give his pupil the chance to make choices for himself. He decides and dictates everything for Sasuke, without listening to Sasuke's input.

As I said, whether or not Sasuke wants to seriously listen to Kakashi's words and advice is totally up to Sasuke. Kakashi could trap Sasuke in a room all day and force him to listen to his lecture on an endless loop, or instruct Sasuke to memorize his advice, or whatever. But it won't do any good unless Kakashi's advice lands on a willing audience. A child tied to a tree is not a willing audience. They are, quite literally, a captive audience.

At the very least, Kakashi should have started off by giving Sasuke a choice to listen or not. If Sasuke ran out of there and absolutely refused to listen to reprimands for his misbehavior, then okay, that's going to require stricter disciplinary measures. But at least give the kid a chance and assess how immature or mature they'll behave before automatically writing him off as a disrespectful kid who won't listen to his sensei. Sasuke has never had problems with lending Kakashi his ear before, so I don't know why Kakashi is suddenly acting like Sasuke's averse to talking to Kakashi for like 5 minutes.

Besides, the fact that Kakashi can't earn something as simple as a child's attention and respect to listen to him for like 5 minutes is...wow. Really speaks to how bad Kakashi is as a sensei and how terrible he is with kids. Even if Kakashi's assumption that Sasuke wouldn't listen to anything he had to say was true (and I'm sure it isn't), it speaks to Kakashi's ineptitude and incompetency as a teacher, because he can't even control one kid. Kakashi has had an entire year to earn Team 7's respect and trust. Yet he has earned neither from Team 7, seeing as he can't even get one kid to listen to him for a few minutes.

Another problem I have with Kakashi tying Sasuke up is that visually and symbolically, Kakashi's choice of physical positioning asserts him as the dominant alpha in this scenario and Sasuke as the inferior subordinate. Through the whole conversation, Sasuke is forced to look up to Kakashi, and Kakashi is looking down on Sasuke and talking down to Sasuke the entire time, a symbolic gesture of condescension.

Sasuke is unable to stand eye-to-eye with his teacher like an equal and has to crane up his head to look at his sensei the entire time, which isn't comfortable positioning for a conversation, especially when Sasuke is already upset and angry.

And whether the characters are aware of this symbolic posturing is open for interpretation, though I personally doubt the visual posturing is completely lost on Sasuke, since Sasuke himself has used his physical positioning on multiple occasions to make a symbolic point, like how he positions himself in the blinding sunlight when Naruto reunites with Sasuke at Orochimaru's lair, forcing Team Kakashi to be "blinded" by Sasuke as they look up at him.

In this case, it puts Sasuke in a defenseless and vulnerable position. With his arms bound, Sasuke is completely unable to defend himself and is rendered impotent and defenseless before Kakashi, a disturbingly compromising position for any warrior to find themselves in. Considering the already-tumultuous state of his mind, this can ultimately only make things worse since Sasuke had just awoken from a coma and a broken arm that his own brother inflicted on him and after his friend Naruto had just launched a unknown deadly jutsu at him.

Itachi's violent appearance especially had reinforced the idea that no friend is truly safe and trustworthy, considering that Sasuke had once trusted Itachi above all.

Sasuke is recovering from Akatsuki-level torture, the same torture that has been shown to drive people mentally insane in the Itachi novels. It's a miracle that Itachi's mental torture didn't drive this 13-year-old child completely insane. One can't reasonably expect Sasuke to suffer through torture of such an extreme caliber and not be negatively affected. Add on to that that Orochimaru and Gaara, high-level shinobi that Sasuke proved defenseless against and has been left at their mercy. Worse, Orochimaru is still hunting Sasuke.

So at this point, Sasuke is tense, on edge, and easily scared, which is not a good mental state for Kakashi to go around casually tying him up. Sasuke is in a flighty mood and doesn't feel fully safe, and Kakashi needed to reestablish trust and security and make sure Sasuke feels safe and calm. Sasuke has been attacked by two of the people he trusted most; he needs reassurance right now, not aggressive behavior.

You can see from Sasuke's startled expression that he's frightened when he's attacked out of nowhere but hasn't yet seen that the ambusher is his own sensei. Wrong move, as this only increased Sasuke's aggression and bad mood.

Furthermore, Sasuke grunts in pain as his back hits the tree, showing that the force Kakashi used to tie him to the tree was rough, not at all gentle. Pretty inconsiderate, considering that Sasuke is still supposed to be hospitalized and he's still recovering from his injuries.