It's simply ethical consistency.
If you are justified in shooting and killing me for going into your home with a gun against your will, and taking your money simply because I have less than you. How can it also be justified for the government to go into your home with a weapon and take your money and give it to me? But in the case of the government, not only are you not justified in killing them, they are actually justified in killing you if you resist or straight up refuse.
Only one can be justified.
In both cases I get your money. But in one scenario you can justly kill me, in the other you will be killed if you don't comply, and both concurrently exists in the US.
Either it is just for a person to take wealth from another who has more or it is not just.
It cannot only be just when it's performed by the state.
Basically. If it is not just for an individual it cannot be just for a group, because a group is only comprised of individuals. Each individual acting independently. Meaning that at some point, an individual would commit an injustice against another.
Government is the biggest scam ever created. It creates laws and then says that they are the only ones who are allowed to break them. Hell, most of the time when the law is written the government is exempt from those laws. Or the very individuals who create laws for you and I, don't have to follow the laws that they, themselves created.
I cannot steal - The government can steal
I cannot kill - The government can kill
I cannot kidnap - The government can kidnap
And if I tried to steal, kill, or kidnap I could legally be killed myself.
But if I try to prevent the government form stealing, killing, or kidnapping, I could legally be killed.
So
what is the argument against wealth redistribution?
It is only just if it is universally recognized and protected. If a government wanted to do it, then it is only moral, ethical, and just if it is a protected means of acquisition for the poor. If you believe that than that's fine. But if you don't believe that theft, plunder, and stealing from someone is justified, even in the case where the "victim" has more, then how can you defend the action simply because it is a "group" committing the theft, plunder, and stealing?