So your premise is that if we build shorter buildings, they won't go after them?
They will go after what we ourselves define as "great". If we define the Rocky Mountians as our national treasure because of some environaut touchy feelgood thing. They will burn down the forest. If we have a Golden Gate bridge, they will topple it.
Just as offering land to the Palestinians encuraged them to send more suicide bombers, because they thought they were "winning". Building a huge, sick, mausoleum on lower manhattan will bring on more attacks.