That thing is ugly and makes no sense in the context of a 9/11 memorial. What do motorcycles have to do with that atrocity, perpetrated by radical Islamists using passenger jets as missiles against the quintessential urban buildings.
The spikes are meant to look like the Oculus, which is a building that is on the site of the former WTC, which includes a communter rail station and a shopping mall.
It is an ugly building that screams "LOOK AT ME!!!"
It has zero to do with the former WTC, and mostly serves as a vanity project for the architect. Plus, if you want to buy your Old Navy distressed jeans in the site of a national tragedy, it's great.