I see the argument for laws and inserting the state when Bill Gates starts showing up and buying children and eating them and so on.
But the size of my slice of pie is not impacted in any way by the size of Bill Gates slice, no matter how big his slice grows. In fact, in my line of work, quite the opposite. His slice of pie has created all sorts of opportunities for me.
I see no evidence of a singular 'The Wealth.' There is no Pareto inefficient side effect, one made less by another's gain, that is attributable to the amount of wealth anyone has earned or created.
The real problem facing this country, and the major issue with wealth inequality is not that some create too much, but that others create too little.
Unless you are Bill Gates' financial adviser, I really doubt you're getting richer because he is.
There's an inverse relationship between a corporate executive's compensation and his emmployees' compensation. That is to say, when employees get paid better, the executives/shareholders make less money. The reverse is also true. So yes, it is absolutely a business' fault if median wage income is falling.
Also, I don't agree that pareto efficiency is the best indication of a nation's well being. While it's certainly pertinent for economic growth, it doesn't ensure that the workers get a lifestyle that is socially optimal.
Consider these scenarios. Would you rather be born into a random family in country:
A. Top 50% make $50,000 a year, bottom 50% make $50,000 a year
B. Top 50% make $70,000 a year, bottom 50% make $40,000 a year
C. Top 50% make $90,000 a year, bottom 50% make $30,000 a year
D. Top 50% make $110,000 a year, bottom 50% make $20,000 a year
E. Top 50% make $130,000 a year, bottom 50% make $10,000 a year
As you undoubtedly noticed, country E is optimal from an economic standpoint. But most people do not prefer to live in country E. People have differing opinions on what's socially optimal. Bernie Sanders just thinks that the US (which is closest to C or D) should look more like country B.
