“He neglects to mention that many of them are actually just retirees. According to Saez and Zucman, whose data Stewart uses, more than 40 percent of all wealth belonging to Americans between and 90th and 99th percentiles is held by the the elderly, meaning age 65 or older. This is what makes wealth data a tricky way to measure class below the very tiptop of the distribution. Stewart’s “9.9 percent” includes a lot of working professionals and business owners with gilded academic résumés, sure. But it also probably encompasses a lot of 75-year-old former accountants and nurses and guys with construction businesses who made a comfortable living decades ago, bought a house, and paid down the mortgage while saving for retirement. There’s no real way to tell a consistent story about who these people are, which makes it a bit hard to blame them for the death of opportunity in this country.”

I don't think the rebuttal makes a fair characterization of Stewart's article. Slate's argument comes down to "Stewart is taking his eyes off the prize, asking us to focus on the 9.9% when the 1% are really the problem" but I didn't interpret the Atlantic piece as implying that those at the very top are innocent in all this. It was more saying that the upper class (9.9%) have been complicit as the top 0.1% have garnered an increasingly vast portion of wealth.

Stewart is asking those in the 9.9% to be more cognizant of those below them, to stop looking up at the 0.1% and realize that the actions they take to improve the outcomes for their children are reducing income mobility.