Why is our personal privacy more important than national security?
If you want to make this argument, you should argue that our privacy is more important than national security (in the context of terrorism) because terrorism cannot destroy our country. By contrast, a lack of privacy and civil liberties can.
There is no way that terrorists can truly destroy any country like the United States. We are too big and too strong to be destroyed or conquered by such means. Therefore, terrorism is not what can be called an "existential threat" to our way of life.
By contrast, an erosion of privacy and liberty can be seen as an existential threat. If we give away all of our privacy and liberties in order to protect ourselves, we will have destroyed our way of life in the process of trying to save it. An America with no privacy or civil liberties is not a true America.
Privacy is more important than national security, then, because a loss of privacy and liberty is more of a threat to our way of life than terrorism is.