Where he is wrong is in effectively claiming that there was no problem with the internal security of the USA against outside threats before September 2001.
There was in fact a huge problem in that basically anyone could enter the country for whatever reasons without being questioned.
While in theory a good thing (it should be possible to have such a system worldwide, and I would love to see that come into being) in practice there are people that are envious of the US to the point of wanting to harm the US seriously.
Such people making use of the open society the US has were what made the horrors of 11/09/2001 possible.

IMO a country protecting its borders by careful screening of foreigners against profiles of people who you do not want to enter is sadly a necessity.
Once such a system is in place (and it is starting to be implemented) internal security measures can once again be relaxed now that the outside borders are secure once more.

Because of the extreme lack of police presence in the US prior to September 2001 just about anything introduced that increases that presence will be seen initially as curbing personal freedoms.
But as the author also states a complete lack of government authority (in the form of police) means a total anarchic society where only the one with the biggest gun survives. I think most Americans would not want that either.

The US security and police aparatus are therefore in flux, they are desperately seeking a new ballance between necessary means to protect the citizens and the increase in monitoring and police powers that that protection brings along.
IMO it will be several years yet before a ballance is struck and only time will tell what that ballance will be.