Basically, he said calling it an equality issue in the first place is the problem. They should frame it instead as a moral issue. Expecting equality of outcome rather than opportunity is where the left runs into resistance from the middle probably and the right certainly.
He's right, lefties don't do the whole morality thing well. Most lefties lean more toward the social libertarian end of the spectrum rather than the authoritarian end. That makes for problems pontificating absolutes about Right and Wrong because morality assumes one has perfect knowledge of what's right and the left usually doesn't go there. So while at least 5 of the deadly sins are wrapped up in most arguments for unlimited acquisition, the left stands there and whines 'yea but, why can't we make everyone equally greedy, gluttonous and prideful?'
They are so hung up on this idea of forced equality of outcome that they seem uncomprehending that it is completely artificial, no one is equal and there are always going to be winners and losers in the real world.
The Zero Sum part:
I think people on the right are more realistic, they instinctively look at the world as a zero sum game. They really do get the idea of "you're with us or you're against us", and instinctively have the "taking care of me and mine" mindset. A generality of course but I think it's pretty obvious that lefties believe there really is such thing as win/win and that we can always be our brother's keeper because the pie will always get bigger. People on the right seem to feel (from my perspective anyway) at least put upon when they are "forced" to contribute to their brother's upkeep and even the general welfare (take the pun as you like LOL). They seem to understand better than the left that you better hold on to what you got.
The economics part:
For a good while there the left could depend on the growth economy to make everyone a winner. It worked because as our energy use continued to grow, we became more more and more productive and the pie continued to get bigger and bigger. But somewhere around the '60s or '70s when we passed the peak of world oil discovery, the peak of US production and the end of $10 oil, we also passed the peak of the growth economy and the pie quit growing.
Since then we have been in a Zero Sum World. Name your malady: from policy choices like Tinkle Down, Deregulation, War on Poverty/Drugs/Terror and borrowing, borrowing, borrowing; to investment choices like building a FIRE economy by offshoring, outsourcing, downsizing, automating, globalizing, temping, and loaning, loaning, loaning. But whatever effect you point to, it is painfully obvious there are now clear winners and losers.
Sure, "wealth" has increased, or the illusion of wealth anyway. But by many measures that don't count the ephemeral, almighty dollar, the US is much less than it was in '69. Life for the majority has declined, or at best stagnated, while the small percentage at the top has done outstandingly well. That is the definition of the zero sum game.
In a declining energy world the game is less and less zero sum and more and more negative sum. Now, "getting ahead" might keep someone else down, soon simply getting-by might mean someone else doesn't.
I leave you with this
Commie website
http://www.truth-out.org/america-decline/1312567242
) that ensure that we rarely feel real pain, worry about staying alive and are cosseted in pain killers when we do contract incurable maladies. We had little to worry about in terms of growing old as there was a guarenteed provision and little to worry about losing the job as you would not starve. 
