Re: The justification for wealth-redistribution.
Charity is for helping the less fortunate and everyone is fully compensated for their labor because it's only worth whatever people are willing to pay for it. Still, there are people who would argue these rationalizations and they are much less unflattering reasons than arguing based purely on greed and envy. When you boil it all down, it really does wind itself right back to the core fact that it is about wanting what wasn't earned; whether it was in wanting to give to others what you didn't earn or to give to yourself what you didn't earn. Or... of course.... asserting that people aren't being "fully paid" for what they do and claiming wealth redsitribution fixes this rampant and imaginary evil. All just rationalizations for why it's right to take what wasn't earned as the spoils of class warfare.
A problem with your argument is the conclusion is based upon very debatable and contentious premises. Your premise "everyone is fully compensated for their labor because it's only worth what people are willing to pay for it" is a very debatable premise and compelling arguments exits suggesting this is false.
You haven't introduced a shred of evidence to support your assertion. All this is and nothing more is "your own rationalization" and nothing more. You have presented an unsubstantiated argument built upon debatable assumptions. It's a pathetic argument.
Your argument assumes people are fully compensated for their labor, and because they are, then redistribution on the notion of helping people because they are underpaid is false. Yet you just declare, without more, people are fully compensated for their labor. There is some very compelling arguments and evidence suggesting this is false for some fields.
A good example is the fact in some industries the final product is sold, in aggregate or individually, for more than what it cost to obtain the materials and assemble the product. So, if a product is sold in the aggregate for $1 million dollars then the value for the labor is $1 million dollars, of course divided by the number of laborers if there is more than one laborer.
Yet we know the laborer doesn't get fully compensated because of the existence of profits. I'm not casting any aspersions on the existence of profits but rather using their existence to demonstrate, as evidence, the laborer isn't fully compensated for their labor. (The aggregate amount made off of the product is a factor in determining whether someone is fully compensated but a strong one).
My point here is your comment as "imaginary" the notion people are not fully paid for their labor is at this point baseless whereas there is evidence, and very compelling arguments, to suggest people aren't fully compensated for their labor. Hence, redistribution instituted to ameliorate this phenomenon.
Then of course there is the compassion and charity component. Helping out impoverished kids who need financial assistance.
I do not rule our greed as a factor but what plagues your argument is your unsupported and at this moment unreasonable assumption greed is the only reason, on the basis of nothing more than "you" can't possibly fathom it being anything else.