That was one of the biggest tragedies in recorded history. Do you even know what it did to the economy? It was like Black Monday on a 5x multiplier.
The World Trade Center, keyword TRADE. This isn't pokemon shit, this is real-world stocks and dollars. The portfolios were ruined.
The next time you laugh at that, think about the human beings that had their vacation bonuses decimated that day. Think about how the economic blow made countries like China catch up to us. Just think about that.
There is a slight difference in quality between a working class person who took a job to help people, or do what they can to survive. Compared to a rich person who works in the world trade center doing marketing to make sure children get as much extra sugar in their diets as possible. Or someone who's job it is to make sure bread costs slightly more so everyonecan suffer and a rich man can get a better yacht. Or any of countless other godawful things that makes the world worse. In an objective moral sense stopping them makes the world better. Each of those people will cause more harm any misery than they could ever justify. Maybe not in as dramatic a way as blowing up a building, but making billions of peoples lives worse and harder for decades will add up to far more harm done than than 9/11 caused. It does hurt to think about because in the west we have been denied any systematic moral or ethical education. A grumble in our tumbles when we think about huge things isn't a sign of ethical understanding however.
Now, add to the fact that all those 2k who died had a genocide done in their memory and the situation become starkly clear.