BROOKLYN - At a packed public hearing Friday, community activists voiced their displeasure with the city?s idea to knock down the Gallery at Fulton Street. The plan calls for a high-rise building that would include 1.5 million square feet of retail and office space, as well as 900 apartments. Due to city guidelines, 180 of those units must be used as affordable housing. Many say the city, which is offering millions in tax breaks to the developer, should demand more than 180 affordable apartments. The guideline at the center of the criticism states 20 percent of housing must be used for affordable housing purposes. Advocates say if the city is using taxpayer money to help a private developer, that guideline should be thrown out the window. The Fulton Street project is just one of several large development projects that are awaiting approval in Downtown Brooklyn. The city rezoned the area in 2004, paving the way for redevelopment.