Its never a logical argument. Its a worldview argument. Its a moral argument surprisingly. The only justification is "because thats the way the world should work". Their framework for how the world works has been molded in such a way that criticism of wealth hoarding is in some way the fault of those making the criticism.
Whenever people say "that's the way the world should work," I see that as an appeal to natural law. Survival of the fittest. When people advocate for a philosophy along those lines, it's a case of "Be careful what you wish for, you may get it."
I don't see it as the fault of the person making the criticism. People can observe and criticize anything they want, as long as there remains the right to free speech. Even if that right didn't exist, people would still find ways to question and challenge "the way the world works," as they have done all throughout history.
If a poor person makes the argument they want free stuff.
If a middle class person makes the argument they are just envious that they aren't as successful.
If an upper class person makes the argument they are a hypocrite.
I think the poor just want to have a fair chance in the so-called "land of opportunity."
The lower middle class (sometimes called the working class) only wants a fair wage for a fair day's work. Low wages combined with high prices can make people somewhat restless and cranky over the long term.
The upper middle class is in somewhat better shape, although they're more driven to try to keep and protect what they have. I don't know that they're "envious" of the wealthy class, although they might feel more vulnerable to political instability or social upheaval.
There are some in the wealthy class who might support liberal social programs and greater equity in society, possibly as a way of hedging their bets. That's the course America took in the last century, as the labor movement and other reforms were becoming more popular. The wealthy classes (some of them, anyway) realized that they'd be better off giving better wages and working conditions to workers.