Because human beings were involved in the 9/11 terrorism acts that brought down the World Trade Center, I think it would be terribly insensitive for any humans to build anything near Ground Zero. We need to think about the victims here, you know. Yes, yes, I understand that human beings were also killed that day; but I think you're just dodging the real issue. Dirty, scumbag humans were behind the plot therefore no humans must be allowed to build there.
It's just that simple.