Many people, especially the families of those murdered by Islamic extremists on 9/11, believe that this is an affront to the memories of their loved ones, and a poke in the eye to America, in general. The city can decide whether or not to sell or lease the property, and they should LISTEN to the people of the city, and of the rest of the country, since the people who died on 9/11 were from all over the US, and the world.
The problem here is that the city does not own or manage the property in question. The building in question (and the lot that it sits on) is privately owned.
I wholeheartedly agree that this mosque/"community center" should not be built. I just don't think that the government (Federal, state, or local) has the authority to decide that a particular religion (or, for that matter, a particular political movement) cannot build a building on land that it owns, simply because of the religion/political movement in question (or even because of the name of the building). The mosque is a bad thing, of course. But, I think, allowing the government to hold/wield such a power is a much worse thing.
Anti-Defamation League Comes Out Against Ground Zero Mosque
http://www.freerepublic.com/focus/news/2561835/posts?page=1
I was under the impression that the land was owned by the city.