This is a straw-man argument well beneath your rhetorical skills. Maybe it isn't your fault - the article you link deliberately mischaracterizes an argument in order to launch on its own wild flight of strawmannery - but there's a world of difference between "economic security" and "well-being."

The poor who worked in Upton Sinclair's The Jungle had, by Piketty's estimation, about the same level of "economic security" as the poor who worked in Molly Ivin's Foster Farms investigation. However, Ivins' crew mostly worked hard at a shitty job. They didn't face imminent mutilation like Sinclair's did. Piketty didn't even make an argument that inequality had stayed the same - he made the argument that the top and bottom deciles hadn't changed much from a quantity standpoint. And he made the argument as evidence for the fact that they'd gone up towards WWII and had come back down. The argument was not that things stayed the same, it's that policies prior to the '70s had improved the standard of living of the poor and policies that began in the '70s were putting it in steady decline.