Do the needs/wants of a stupendously large number outweigh the needs/wants of the merely huge number?
Yes. That's just basic math. More is more than less, and less is less than more.
Also, you talk a lot about sacrificing for the greater good. The stance of the left generally is not that anything should be taken away from anyone, but rather that new resources should flow towards those who need them.
If there's a table with 99 starving people with empty plates, and 1 fat guy whose plate is overflowing with food, and you bring in a cart full of food and just park it next to that fat guy, and you don't see anything wrong with that picture, there is something wrong with your moral compass.
from where did that new cart of food originate? Most on the right would say that if the already "wealthy" person made it themselves (or paid for it to be made) then it's perfectly fine that the food would only be delivered to them.
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Other subtle questions - what level of inequality is "tolerable"? Unless you argue that everyone should have exactly the same amount of wealth, that means there is some ratio on the spectrum between "everyone equal" and "1 has everything, the rest have nothing" that is acceptable. How do you know you've achieved optimum?
The example was deliberately oversimplified to demonstrate the fundamental precept that should serve as a guiding principle when determining appropriate protocols in more complex situations. The intention was not to be an argument for absolute equality in wealth and privilege regardless of individual circumstances, as that path is certainly problematic in it's own way. But since you've asked for more details...
The fat guy is the land-owner, and the starving people are the laborers who actually work on the land. The food does not magically appear, but rather there is a governing body of elected representatives from many farms who keep the farms safe and stable, and take a portion of the food created on the farms to feed themselves and their guards and other associated parties. A newly elected leader in the governing infrastructure has decided to tax less food from the farms, which he can't really afford to do, but he's doing it anyway. He had a choice, to take less food from the fat landlords, or take less food from the starving laborers. He decided to go with the former option, in hopes that the fat landlords who already have far more food than they can possibly eat and yet share none of it with the starving laborers, might finally decide to share now that they have a little bit more.