"It's stealing from the future, locking up prime real estate to be a monument to the past."

Stealing what from the future? Are you assuming that people from the future would rather have a shopping mall or something on the Île de la Cité rather than a monument to the past? Personally, I'm rather grateful that people in the past have taken the time to preserve buildings from their time and earlier so I and others in my time can appreciate them rather than tearing them down and building some disposable modern structure that would be gone now. Not only is Notre Dame in particular a great work of art and much more attractive than any glass and steel structure (of which we have far too many imho,) its connection to the past is something that becomes more valuable as time passes. If we were to tear it down today, you can bet that future generations of Parisians would be cursing our generation's arrogance and self-involvement.

Building a mall would be more in keeping with the original intent. Remember, Notre Dame is on prime Paris real estate because the church served a critical role in peoples' everyday lives back then. Today, Parisians are increasingly irreligious, so it no longer serves that purpose. So that prime land was dedicated to an important civic institution. Now, it's dedicated to what is primarily a tourist attraction.

"Stealing the land. If we built a shopping moll there, future generations could build something significant to their society."

They can still do that. Not tearing down a building today does not prevent future generations from doing so if need be. The only choice today that steals from the future is razing the structure because that's the one thing that cannot be undone.

You want Paris to become like Detroit? Those tourists pump an enormous amount of money into the local economy and help keep the city what it is. No one ever travels to cities like Detroit or Buffalo because there's nothing there worth visiting, and the local economies are terrible.

No they don’t. Tourism accounts for just 2% of the Paris region’s GDP. Their GDP probably would go up if they got rid of their historical preservation rules, allowing more productive use of existing space.

How is it stealing from the future? The future can raze it if they want. Razing it now is stealing that option from the future.

In another comment I quoted Roger Scruton who wrote about the desire of "all forward-looking architects from Le Corbusier to Richard Rogers, of razing Paris to the ground and rebuilding it in concrete, steel and glass" but I didn't expect to see someone actually arguing for the perspective Scruton was lampooning. I suppose he was not exaggerating as much as I had thought.