Since when did the argument, "This should be banned because it's offensive and hurts our feelings!" start earning a place in any kind of rational discourse? Is sensitivity a prerequisite for freedom of expression?
Singling out Muslim Americans, much as with prejudice against Jewish Americans and Catholic Americans before them, will prove to be wrong. The question is how much damage will be done before the fear subsides.
The head of the AJC is all for building the center if it addresses some "concerns." It's like me saying that I will endorse Glenn Beck if he would just address my concerns about his right-wing politics.