The problem with this line of argument is that relative poverty is a problem as well as absolute poverty. To pick the most obvious example, huge inequalities in wealth inevitably give rise to huge inequalities in power and influence, which can subvert democratic government.
Also, what rising tide? In the US at least, real incomes are stagnating or falling for most people.
Also, what rising tide? In the US at least, real incomes are stagnating or falling for most people.