The World Trade Center was destroyed by terrorists who happened to be Muslims. The Alfred P. Murrah building was destroyed by terrorists who happened to be military veterans. The vast majority of Muslims and veterans are not terrorists. An Islamic center in New York City will be as harmless as a VA hospital in Oklahoma City.
The proposed center does not present any substantial threats to national security. Terrorists do not ask permission from the New York City Landmarks Preservation Commission before demolishing a building. No competent sleeper agent would spend much time hanging out in a $100 million building with a big sign that says "Islamic Center" out in front.
Instead, the arguments against the proposed center stem from matters of "sensitivity". It would seem that political correctness is no longer the sole domain of the left.