How is letting someone build a bigger house for his family even remotely comparable to genocide? The city is basically telling his family that they are not welcome, this building is more important than them and they should leave.

The argument was that preservation is "stealing from the future." Ergo, the commenter apparently believes in earnestness that a personified "future" has an unqualified right to destruction. The argument as presented is sheer nihilism, and pointing that out was the goal of my comment.