Can I ask an honest but apparently naive question? What's wrong with gentrification? I thought it was when a neighborhood got cleaned up, and made to look nice? If I understand correctly, they WANT neighborhoods to not be nice places?
Gentrification not only brings in new, paler folk to fix up run-down property, it pushes out the existing darker population.
It is not only a pricing deal like MillCreek wrote, but gentrifiers (especially second wave) organize and insist on better "public services." That is gentrifier-speak for "more cops arresting criminals." That also pushes the previous inhabitants out in large numbers as previously tolerated criminality is no longer tolerated.
So, local "community organizers" seek to head that mess off at the pass. Because their sort has ended up without much of a community to organize after a decade of gentrification.