The 9/11 attackers exploited the existing rules and regulations to take control of those planes. All the security theater in the world won't prevent that from happening again.
So what would you suggest we do? Drop all security altogether?
This may mean nothing to you, but I agree that some of those rules are indeed rather silly (such as the thing about liquids). That doesn't mean that all security procedures are automatically invalid, though.
Take this scanner, for example. It can be used without inconveniencing people - all you do is walk through the thing. And since your face is hidden, the image is rather washed out B&W, and the person looking at the picture can't actually see you as you walk through, there's minimal invasion of privacy.