The main argument from the OP is "how to keep supply-side economics thriving"?
On the one hand, the U.S. is a capitalistic country. No doubt about it. This means that once an individual finds that magic formula to bring his product or service to that marketplace, is able to harnest the power of politics and/or the tax code in order to gain more wealth, the pure capitalist will take every advantage possible to bring about more wealth unto himself.
Problem: Once the majority of industry lay in the hands of a small few, it becomes increasingly difficult for others to jump into the market. Put simple: the big fish quickly gobble up the little fish either through out-pricing them or buying them out. But that's on the side of dwindling competition. Consumers are the bigger threat to perpetual profits.
What we've had take place in this country is two decades of union busting and off-shoring in order to keep labor cost down, and four decades of favorable (low) tax rates for the wealthy. The argument being so that companies can "keep more of what they earn and, thus, put more of their profits back into their business(es)". What entrepreneaur or small business owner wouldn't be in favor of these "cost-saving measures"?
Problem: When your economic policies are based on consumption (and debt) - supply-side economics - you need to ensure there are:
a) enough consumers to keep buying the products and services the marketplace provides, or,;
b) enough investors to take on your debt (bonds) or remain confident in the strength of your company (stocks).
Lose either and profits will fall. All Buffett, Unz, Hanauer, Silberstein and Hindery are saying is "if our capitalistic way of life is to continue, we either need to fulfill the tennants of 'trickle-down (supply-side) economics' or feed the welfare state and stop complaining about it."
Many people out there just don't get it, probably because they don't want to. I'm not suggesting that the wealthy need commit to altuism and give just because. There is a logical reason for raising the minimum wage in a capitalistic society. You simply cannot keep wages so low that it becomes increasing difficult for people to have their basic survival needs meet. The problem with the conservative mind-set is it makes a false argument. It lumps too many into the "lazy" category without acknowledging that there are many people out there who want to make a way for themselves and/or improve their way of life, but they simple can't because they struggle to have their basic survival needs met. These same people who condemn the poor fail to acknowledge that job/skills training does have a cost. A college education - even a training certificate or associates degree - cost! And if you're struggling to put food on the table, a roof overhead, keep the lights on, put gas in your car, or your losing work hours to stay home and care for a sick child or have no health insurance at all, chances are you'll never be able to afford the necessary skills training (college education) to move up from your present status in life.
Or course, some would then argue "work hard and move up the ranks". Easier said than done when those near retirement won't leave (or can't afford to retire themselves) AND your company isn't hiring/filling vacant positions OR just "right-sizing". Fact is, there are many problems with our national economy, but the best immediate corrective action all businesses can take to start turning things around is to pay their employees a higher salary (those deemed worthy enough anyway).
There's only so much the working poor can take. Moreover, the middle-class can only be squeezed so much. Eventually, people will rise up. It's just a matter of time.