Circular reasoning.
One of your problems is that you're trying to simplify the situation into "if this broad thing, then this narrow thing follows" whereas these determinations are based on the totality of the situation. There's a big difference between having a firearm pointed at you in an obviously threatening manner, or defensively when you act in a threatening manner, or haphazardly where the wielder does not have a good understanding of firearm safety, and so on. And there are going to be countless secondary considerations for any one concrete case. Reasonableness isn't a binary thing, it exists on a spectrum.
In any situation where someone did point a firearm at you however, regardless of whether in a threatening, defensive, or neglect manner, you would be more justified to shoot them within, or immediately following, the fraction of a second where you felt threatened than if you were to start chasing after them on foot. That's not to say that chasing after them on foot would never be justified. It certainly would be justified to pursue the Christchurch shooter, for one.
At this time there is no strong evidence that Kyle threateningly bared his weapon at Rosenbaum though.
Circular, and very dumb. Next time you see someone open carrying an AR, why don't you go ahead and charge at them and grab for their weapon? The fact that you would end up ventilated isn't proof that you had to attack.
All the people Kyle shot were at very short range.
I disagree with the assertion that Kyle was "running around pointing a rifle at people." And I wouldn't use the phrase "established himself as a deadly threat." I will say that some of the people chasing after Kyle, not knowing the details of his encounter with Rosenbaum, and only hearing about an active shooter, would be justified in trying to apprehend him, just as Kyle was justified in defending himself from being lynched (with members in the crowd shouting things like "cranium him") after exercising self defense against Rosenbaum. This is one of those instances where both sides can be justified. I don't know if I would extend that to Grosskreutz since Kyle told him he was going to the police. If anything, Grosskreutz is especially vile for helping to rally the mob to go after someone he knew was surrendering.
It all depends on motivation. If you're open carrying to act as a deterrent, then there is no similarity at all. Usually, you don't find yourself in a situation where you are "required" to use your weapon against unarmed individuals, because those individuals know better than to attack someone who is open carrying. That's the point of open carry. In the one-in-a-million chance you find yourself charged by a psychotic pedophile who was just discharged from a mental institution, you may have to use that weapon, and if you find yourself squared up against such a lunatic, going unarmed might end even more poorly.
If you go armed hoping that someone will give you the excuse to shoot them then that's premeditation. If you admit as much you lose your claim to self defense, which has happened to a few people acting "tacticool" to responding officers.
Rosenbaum would be charged and would have no reasonable claim to self defense. He's also a repeat offender pedophile. The book would be thrown at him.
Grosskreutz would have a very, very, strong self defense claim if Kyle hadn't told him he was surrendering to the police. But because he did, it would be tough. Maybe not impossible though.
Huber would depend on how he killed Kyle. A single lucky blow to the head with the skateboard? Very strong. Repeatedly bashing Kyle's face in with skateboard until he expires? Much less strong. Disarming Kyle and shooting him? Depends on whether they were still struggling over the gun or not, whether Kyle was trying to regain possession, etc.
Rosenbaum and Grosskreutz had the worst of intentions, but yes, Kyle's state of mind is (or at least should be) the determining factor. You may want to consider the fact that if Kyle had gone into Kenosha looking for an excuse to kill people, the mob that chased after him was a target rich environment. He only shot at people who were an imminent threat to him. He didn't mow down the mob indiscriminately. If he were looking for an excuse to kill people, he should have.
There is nothing "circular" about what I said. And YES ... He was teenager running around with a long gun he wasn't legally allowed to have pointing it at people. Underaged Kyle had no reason to be there with a firearm. He was PERFECTLY safe at home. He should have just kept himself home. His actions directly and indirectly caused the death of two people and wounding of a third that should be alive today if not for inserting himself in a volatile situation he should not have been in. Where people can purposefully gear up and place themselves into situations where they can be forced to shoot someone - "legally" kill. He intentionally put himself there and reasonable people are calling him out.
There seems to be some veiwpoints -
Viewpoint A: Someone in such a situation with a firearm is by default seen as a "good guy with a gun". The assumption is that if that gun was fired, then it was for a “good” reason and to prevent something bad. Anyone attempting to disarm said person with a firearm is obviously up to no good, and full self defense mode including killing the attemptee is warranted
Viewpoint B: Someone with a firearm in such a situation is by default seen as someone to at least be wary of and potentially a hair trigger teenager with a gun in his hand looking to use it. Teenager with a gun in his hand shoots someone, and the immediate assumption is that teenager with a gun in his hand has been confirmed to be a bad actor that could easily be shooting other people. Hence a potential active shooter, and as said teenager with a gun in his hand just shot someone in front of witnesses, the potential to be an active shooter is significant. Fight or flight reflexes kick in amongst those in the crowd.
It's Rittenhouse’s responsibility to determine whether those gunshots were actually a threat to him before opening fire on someone who wasn’t even carrying a gun. This is something any competent gun owner should be able to do. People are saying this kid opened fire because he was scared. But if no one was shooting at him, he had no valid reason to be scared, so he was defending himself against an imaginary threat – he did not have the maturity, judgement, or competence to be carrying a weapon in a potentially dangerous situation.
He went to Kenosha to ‘defend a business’. With a gun he seemed to have no problem acquiring knowing he no business being there and no experience in that type of situation. Fifteen days prior he’s on video saying he would like to shoot some men who were shoplifting. Reasonable people will continue to question the idea that he went there for any other reason than as an excuse to shoot people.