I think you’ve taken the right-wing bait a little too to heart here. In the US, most young people, most women, and most ethnic minorities are Democratic-Learning, and I’m speculating those are also the groups most affected by poverty.
However, extrapolating that to the OP's point of:
> the average leftist/Democrat in the United States has no idea what it's like to be poor and reliant on many public services
really doesn't follow at all. The numbers are clear that really poor people heavily skew Democrat. In summary:
Less than $30k: 20%R to 43%D
$30-50k: Equal split
$75-150k: 33%R to 30%D
$150+: Equal split
It feels impossible to go from these numbers to the Op's conclusion, although I would accept the modification of it to "the average person in the United States, of either party affiliation, has no idea what it's like to be poor and reliant on many public services". Suggesting that's more true of Democrats is simply not factual, the numbers suggest though.
More detail at: http://www.people-press.org/2016/09/13/2016-party-identifica...
The term “white flight” is a nonsense, ideological term only used by a very fringe group.
Real economists and analysts talk about globalization, inflation, trade, shift from manufacturing to service economy etc. the things that are most harming African Americans and Hispanics are not Dollar General stores.