People love to drag San Francisco — and maybe rightfully so. A majority of its own residents bash the city in polls for its homelessness and open air drug use, but a new ad campaign is looking to fix that. Funded by the tech billionaire sons of Gap Inc.’s founders, the “It All Starts Here” campaign is promoting the city’s history — cable cars, Levi’s jeans, Harvey Milk, the Summer of Love — on billboards and internet ads. There’s precedent for this: In the 1970s, suffering a similar poor perception, New York City hired the esteemed Milton Glaser to help. He created the iconic “I Love NY” logo.