I think the 'rich must help the poor' argument, is actually taking the whole thing one step too far.
'Everyone for themselves' runs counter to the most basic instincts of the human species. It's not about advantages and disadvantages. It's about teamwork. Sometimes, this takes the form of redistribution. Be it a potlatch or a progressive tax plan. The only difference when it comes to government is scale. Due to the impersonal nature of larger groups (i.e. nations), that group can no longer depend on the basic human instinct to help those they know.
You can accuse redistributive taxation of being an oversimplification, of being chosen because it 'feels good' or is easy for 'the masses' to understand, but it's ultimately necessary. It's simply a larger, more complex iteration of
basic fucking teamwork. And when your team has 300 000 000 people on it, some of them won't always like the way that works out.
But perhaps if you don't like that argument, and think that teamwork has no place in the country that is the worlds greatest shrine to rugged individualism, I'll offer you some good ole' pithy Americanian phrases instead.
United States.
United we stand.
The Union.
One nation.
We the people.
"We must all hang together, gentlemen...else, we shall most assuredly hang separately"
Spah's sappin' mah income