But it's also entirely possible that stores do this sort of thing all the time with the blessing of city councils and what it does is displace the existing population. Dallas (where I live near) is notorious for giving developers tax breaks to tear down lower class apartments if they agree to build something of much higher tax value. I doubt Dallas is odd man out.

I'd guess that's exactly the worry here. Installing places like Trader Joes, which have the impact of attracting the more well-off, causes a gentrification feedback loop, raising the cost of local housing and ultimately displacing those that can't afford it.