Americans as a group do not like Islam, because Islam is in many ways the antithesis of our culture. We like our women to be pretty and interacting with men in our society, they like to uglify theirs and keep them at home. We do not like the idea of a single religion, and are especially unfond of a religion that believes it has the right to wake up every bloody soul at dawn every day, and pray in unison fiver freaking times a day at a time set by the local mosque. We have tried to put religion in charge of our society.and it resulted in a thousand years of extreme ignorance and backwardness, and Islam is certainly no different from medieval Catholicism in that respect. The main difference is that the Holy Mother Church had one Pope and Islam has a variety of conflicting imams and ayatollahs.
I find it pretty weird that somehow the most valuable parcel of real estate in the country should be, in the opinion of some Capitalist Americans, declared "holy", "sanctified" and "sanctified" and therefore off limits to religious use, though. The people who died on 9-11 did npt die as martyrs, valiantly defending their noble cause. They were unsuspecting and unlucky victims, period. 9-11 was not Gettysburg, or Valley Forge or even Pearl Harbor, so let's get real.
Let them build their damned mosque and then we can all ignore it, just as we ignore the fundie handing out Jack Chick Comics or the Jehovah's Witlesses peddling their religion like the freaking Avon Lady.
I am pretty sure that we can enforce laws against annoying calls to prayer five times a day.