So you are saying that 1) we need citizens to assume the mantle of the police at their whim to maintain law and order, and 2) that angry white men are not responsible for most mass shootings in this country. Interesting take. Seems you want the wild west. I am glad we live in a society where you would not be making the rules.
So yes he was ambushed. Ok. If he hadn't been there at all, or hadn't had a gun, would anyone have felt they had a reason to ambush him? You are acting as if his choice to be a vigilante is fully reasonable and justified, and that he was the only one capable of being a vigilante.
Here is another way to look at it. Rosenbaum went there to stop shooters from attacking the protesters, with a plan to take out any bad guys by any means necessary, you know, as a vigilante. So he sees a kid brandishing a gun, an obvious gun, waving it around out in the open, like those used in mass shootings. He devises a plan to stop this dangerous shooter, since someone needs to maintain law and order, as you said. So he determines the best way to do this while being as safe for himself as possible, and he "ambushes" him, intent on stopping the guy with the gun, and not believing him while he yelled at him that he was a friendly, I mean that is what the bad guy would say, right? So he tries to stop him and the bad guy, the active shooter, shoots him. Who is the vigilante here?
You act like since Rittenhouse went there with a gun he was automatically authorized by the police to meet out both sentence and execution on any situation he deems to be dangerous that needs to be taken care of. This is so ridiculous it is mindboggling anyone could put that forward as a reasonable response. We do not live in the wild west. We do not live in a third world country where it is bouncing between tin-pot dictators. We live in an actual country with rule of law and law enforcement personnel and everything. We have no need of vigilantes.
It is hard to believe we have to state this stuff to adult human beings. Scares the **** out of me for where we are heading as a country. Which president will be the one fiddling while Washington burns?
Edit: the plinking argument is one of the worst excuses I have ever heard. So he innocently took a gun to the protest, not to hunt anyone down but because he got lost on the huge tract of land and had to find some cans to plink somewhere? Wow, the leaps in logic are astounding.