Earlier quoted context omitted.
Passing a law like that means they'll put in the infrastructure to actually do it. If things deteriorate significantly in the US, it is likely that attempting to gain the ability to shut down the internet would directly trigger some sort of civil unrest while now it only triggers angry blog posts.
I am at a loss as to what this additional infrastructure really permits that having lots of armored men with guns does not. Armored men with guns are a flexible bunch, they can do lots of things. The marginal distinction to the person in power between pressing a button and ordering other people to go shut the net down is pretty minimal; it's not like without this switch, the President is going to actually have go out…
EDIT: removed Emergency Broadcast System analogy.