The fight to protect San Francisco’s cultural enclaves against gentrification and displacement typically takes the form of opposition. Activists show up at public meetings to decry upscale housing, to bash new office towers, or to disparage chain stores or fancy restaurants catering to well-heeled newcomers. But the speed with which these neighborhoods are changing suggests that it hasn’t been working very well. Now Supervisor Hillary Ronen is betting that those fighting to save what’s left of San Francisco’s cultural districts would be better served by saying yes. “We all agree that gentrification is happening — everyone is on the same page there,” Ronen said.