Does it actually say "7 days worth of food"? There's no way of determining how much food is a "days worth." I could eat less food a day averagely than someone else and vice versa.
But, we all see the connection there, right? Food storage is the first steps on the road to terrorism! One day they're eating a sandwich and the next they are out blowing up buildings.
As for the bill, I'm not really sure how to respond. From what it sounds and from what I've read, they are in a state of worry. Congress is probably afraid of a civil revolt that may develop from all the protests, so they are trying to ensure that anyone they classify as a threat can be easily and legally taken in. How vague it is could be abused, but at the same time it could be argued against and eventually overruled. Plus, there still is a chance that the Supreme Court will say something.