I think you need to step back even farther: what is the point of money? If you don't have a good answer to that question, how can you reason about the benefits and drawbacks of different ways to distribute that money?
I'm going to out on a limb and suggest that the point of money is economic growth. This may seem like a circular argument, so let me expand on that a little. Imagine you have a farmer. This farmer wants to grow food and he has plenty of land. However, he does not have enough seed to plant all of his land. He has nothing to barter with until after his food is grown, so he ends up "wasting" part of his land (letting it go unplanted) because he could not get enough seed.
In this scenario, everybody is a loser. The farmer grows less plants and will not be able to barter for things he needs in the future. Society also gets less plants. So it makes sense to give the farmer more seeds so that he can plant his whole field. In fact, because he can do that, he can repay the favour in the future by giving up some of his fully grown plants.
Money is a kind of token that can be used to trade for things. It is very useful for society to give people money if they will use it to trade for things that they need, which will in turn produce things that will improve the quality of living for everyone.
Money that is piled up and not spent is not helpful to the economy or society. If there were a limited amount of money (and in some ways there is), then we could say that people who hoard money are a burden on society because they stop people from making use of that money to improve society. Ideally we would split up all the money in the world and give whatever amount is needed to the people who would be able to use it. In a really ideal world, each person would be motivated and able enough to spend the money in a way that would produce benefit for society.
Of course this is not the case. There are many people who hoard money (bad). We can also see that there are people who would spend money improving the beer brewing industry (maybe not so bad) at the expense of investing in life saving medical research (arguably seems better than beer in some ways). In fact, quite a lot of people simply want to consume goods and distribute money around, as opposed to trying to improve things. Those people are at best neutral to the system, though better than the hoarders.
From a societal point of view, it is best to distribute money in a way that maximises people's ability to use it beneficially, while minimizing people's ability to hoard it or distribute it arbitrarily (buying shiny useless toys or food/shelter that they don't need). So already we can see that depending on what people want to do with money, it is beneficial for society that there is an inequality.
Having said all that, I think that the inequality that we have reached at the moment is far from ideal. Now the really interesting bit is that what I wrote so far seems to favour a fascist economic system. I suspect we can do better, though ;-)