Well it’s just stupid to be blunt. Nobody says oh I work at ground zero or I get the train from the ground zero station or I’m going shopping at ground zero. Ground zero refers to the location of the event and it’s aftermath when it was a giant hole where they were still finding body parts for years after, not what is there now. People who lost family members still likely have to interact with the WTC area regularly and if you asked if they’re going to ground zero today it’s like asking if they’re going to a grave yard where their family died. You don’t live there or have anything to do with it so if someone says it’s insensitive and you telling them it’s not is like telling someone not to be offended at someone being an asshole just because they didn’t mean to be offensive. It doesn’t change how people who live there perceive it just because you don’t mean it that way.