Yes, the events with occurred on September 11 were controversial, because they were horrific. There were people who thought that murdering thousands of innocent people would be a good idea. It is controversial to want to kill innocent men, women, and children, and it must take a broken frame of mind to reach the conclusion that such behavior is acceptable.
When I first heard about the events on 9/11 my heart immediately went out to everyone who lost their lives or a loved one. However after hearing all of the side stories and back stories, I can see why many people find it very controversial. I can understand the families of those lost want to drop the whole thing and move on but I can understand why others have a hard time believing the "true" story put out there by the government and media.
Building seven looks like it was destroyed in a controlled demolition because of the way it collapsed which calls into question a planned incident and is one of the most popular pieces of evidence of a controversy related to Sept 11.
However, he theory of planted thermite charges in the towers and the disbelief that the jet fuel caused the towers to fall is another big one.
This marked the first time since Pearl Harbor that the US was attacked on its own soil. The series of coordinated attacks and the huge amount of casualties and damage that occurred were , of course, very controversial. The attacks were planned to be devastating, and they were. It's one thing to attack a military operation, but these attacks hurt and killed civilians from many different countries and left a lasting change to the New York City skyline.
The events that occurred on September 11th, 2001 are somewhat controversial, given that there are some that theorize that they may have been put together by the United States government or some how planned to happen, outside of terrorist cells. Some people believe that in conjunction to the planes hitting the tower there were also bombs in the basement floor as well. This is documented and easy to find on the internet.
When it comes to the horrible tragedy that happened on September 11, 2001, I really do not think the events were controversial per say, but I do think they were absolutely horrific and terrifying to say the least. 9/11 is an event that the world will never soon forget as long as we live.