Ready for wall of text?
K, first of all, people need to know the facts about the Mosque before making assumptions.
It's not on ground zero, it's 2 blocks away, I wouldn't want any building other than a memorial built there. Second, this is in no way an extremist mosque whatsoever. The Imam there writes articles denouncing fundamentalist Islam, and all religions in their fundamentalist form. It's not going to be only a mosque, it's a community center that ANY New Yorker can visit, it simply has a prayer room for Muslims.
If you say there can't be mosque on ground zero, can you not also stop the building of Churches in Jerusalem and every city the KKK operated in? They committed atrocities in the so called name of Christianity.
And finally, it denies people of their most basic rights. Even if you're not Muslim, and you hate every Muslim, Moderates as well as the very small group of extremists, this will hurt you. It lets the government and the general thoughts of the public decide which parts of the Bill of Rights applies to you.