Korra has never followed through with any of her terminal/implied violent threats on defenseless people in the entire series, see Baatar as the final example. You can play a logistical what if game with the road scene and his driving, but that runs contrary to the established tone of the show. This is a show where Tenzins air bending magically knocks enemies away to adjacent roof tops in season 1. Korra is the Avatar, if something had happened to his car she could have easily used her bending to save it. Neither her intent nor the authorial intent of the scene was to show he attempting to place his life in true jeopardy.
Also by the simple fact that Korra isn't a killer; she said to the judge 'If you kill these people, I'll kill you' in a moment of shock and anger, but threats and reality are very different things.
Here, you're playing the "it wouldn't have happened because the author wouldn't have made it happen" game. Korra never followed through on her threats because they always gave in or something interupted her. Bataar is Korra post character development, where she specifically talked how 'back then, I'd have wrekt ur shit boy, but now I'll just blue ball you'. Meaning here, she'd have followed through, if she had to.
But yes, you're right. It wouldn't have happened. If Korra had tried, something would have interrupted her. If the car had swerved off the road, it'd have landed on a magical patch of land where the guy couldn't have been harmed. If Korra had told Naga to rip the guy's face off, Naga's teeth would have spontaneously faded from existence. Because, in this show, the main character of a children's cartoon isn't going to murder anyone.
But that doesn't change that her character, by all indication, seems to have been intent on trying it. She DID attack him recklessly enough that, logistically, he could have died had he just not been lucky enough to swerve to the side. You can't make stuff up of what could have happened to try and prove your point.
Or she realized the evidence was weak and just yelled threats because that's how she was in season 2 a hot head. Your defense is that the protagonist would simply ignore obvious information that was clearly communicated to her and the viewer prior to the trial, and that doesn't hold up.
She absolutely was, she saw that the evidence to convict her father wasn't enough and believed that strongly enough to simply go to him and say 'I'm going to bust you out', he says no and she agrees not to do anything rash until she sees her mother breaking down, so she goes to the source of the issue the judge, and tries to get information from him.
This entire argument is predicated on the idea that Korra is far more intelligent and savvy than anything we've seen indicated. It begs the simple question. If Korra saw how obviously circumstantial this evidence was, why didn't she just point it out? You're saying it's because she's somehow intelligent enough to see how this is bullshit, then later in control of her anger enough that she can easily threaten to run a guy off the road and maul him with her dog but never actually go through with it. But she's somehow too angry to even say "Well, this doesn't work because inteliigent reasons"?
The simpler and (and more consistent throughout the series) explanation for why she can't make that counter is the obvious: She doesn't know how. Korra is just not a thinker. Logic and argument is a foreign nation to her. She knows it's BS because her personal experience, and what frustrates her is that she can't prove it. Because it'd be one thing if she was pointing out how this evidence does not work and the judge was hearing none of it, and another for the oppostion to present flawed evidence and her to jump to rage and anger without even trying to point out how it's BS. Look, this is something she does the entire series. She doesn't make an argument for why Zaheer is wrong, he's just wrong. She doesn't make an argument for why Kuvira is wrong to take Zaofu, she just is. Hell, she couldn't even make a good argument for why Ryu should be an airbender. She didn't have an argument for Amon, and she didn't have an argument for the equalist she meets on her first day in republic city. Korra trusts her intuition whole heartedly, and is baffled at multiple points where her opponents don't fall in her line to her way of thinking just because she told them to. You're saying this is the one instance where she is perfectly aware of the logical flaws of the opponent's case, and doesn't say the exact thing that might get her parents off the hook because she's too angry that her parent's aren't getting off the hook?
I don't really want to get into a philosophical debate here, because it goes nowhere every single time, but saying something is "immoral" really doesn't mean anything. You're basing it on a scale of good and evil and that scale is different for everyone.
Me personally? I don't think Korra would have killed him. I think she'd beat the shit out of him and leave him on the side of the road battered and bloody, but she wouldn't kill him. I don't think so, anyways.
By that logic, no one can ever say anyone ever did anything wrong. There are plenty of ethical theories to choose from, so you're right, but I disagree that it doesn't mean anything.
I'll concede that she would never come in with the intent to kill him. But in her anger, it could easily just slip. That's what anger basically does.
Regardless your original supposition that Korra thought justice had been carried out or that the trial was fair has no basis. She clearly believed that her parents were innocent based on the information she had prior (that's why she yelled it out after all!) and that is why the judges conduct and then sentence provoked such a strong reaction out of her.
No, my original proposition was that she believed it was a fair trial. She knew her parents were innocent because the guy who actually tried to kidnap unalaq said her dad wouldn't go with them and she found her parents in their home the morning after the attempt. My original proposition is that she doesn't believe the trail was rigged. Merely that it was in error. And while that is objectionable as well, my point was that she was willing to risk killing an innocent judge that she has every reason to believe merely upheld justice to the best of his ability.