There's no single motivation for this. But I think the motivation we can derive using mostly just logic is that it'll benefit all the human race, including ourselves (who are not the ones starving). After all, less people starving means more people producing, creating theories, etc.

Inequal distribution of resources

For now, we can strive for a bare minimum of clean water, 2000 calories a day of food energy, and governments that don't stifle economic advancement. We have plenty of resources to do this now, but it isn't happening because once wealth and capital get concentrated in individuals or groups of people it tends to just make them more wealth.

And the answer to the why is that I believe humans have a fundamental right to life. I have no real justification; it just feels right to me.

Funny thing is: people who live in countries with higher levels of equality (think Japan, Finland) are the very same countries with high suicide rates.

Not saying that correlation implies causation, just to show that perhaps this ideal equality is not so fundamental to our overall happiness.

Also, I'd like to know how we can strive for clean water and food for 7 billion people (9 billion until 2050) while keeping civil liberties to people along the process.

The economy is not a zero sum game.

Perhaps not for equality, but at least a healthy baseline. Everyone deserves to live

Great. We agree on that. But how do we achieve that? Taking from the rich and giving to the poor? Never in history this worked.

On the other hand, whenever you have an environment where those who produced wealth were allowed to keep it, you'll see general prosperity.

The problem is: who's producing wealth? In Brazil, you can argue that a factory pipeline worker is the one producing the wealth, yet he's able to keep but a very small percentage of what he produces.

Arbitrarily taking wealth from one and giving it to other's is not really good idea, I agree with you. The "how" is the whole problem. In my opinion it's the biggest open problem of human kind.

Sorry, but no. What differentiates the factory worker from Brazil or India or Malaysia or Sweden? Nothing. Why should there be any difference in what percentage of the final cut is his? Is the Brazilian factory worker able to produce more wealth without the machinery, equipment, marketing people, product designers and everything else that is part of any supply channel? No, he isn't.

The problem in Brazil is precisely this mentality that keeps us with a half century old labor code and absolutely zero incentive for entrepreneurship.

The Welfare State is dead, see http://workforall.net/ScandinavianModel.html

The rich and powerful themselves have to decide to help the poor.