White flight. Others in the neighborhood will also move away from the racial expansionism, violent attacks and other increasing crime and deterioration.
Oddly enough Mount Laurel did try to demolish an older black neighborhood back in the 1960s to make it more attractive to suburbanites back in the day and got smacked down by the courts in doing so. It was a clear case of using eminent domain and zoning to racially exclude people in that case, however: https://en.m.wikipedia.org/wiki/Mount_Laurel_doctrine