Why is the unequal distribution of wealth problematic? Because it can destroy democracies.
Right now, the top 1% in America pay about 40% of the tax revenue. Far from being shining philanthropists, the reason for this particular distribution is because the top 1% make so much more money than the bottom 99%. Such a massive concentration of wealth allows rich people to single-handedly finance PACs; to use their influence to raise money quickly for their preferred candidates; and to buy all-important television airtime for their preferred candidate. As a result, modern-day candidacies require fewer people and more mass media. A candidate no longer needs all corners of his/her jurisdiction to ascend to political office--a few well-off friends can introduce a potential candidate to an entire jurisdiction by buying television ad spots.