the need to cut off the internet makes perfect sense IN THE RIGHT CONTEXT. which is what the law will be tailored to. but if you take the idea of shutting down the internet, and put it in the context of your deepest fear: say, censorship based on political ideology, of course the idea is frightening. AS IF THIS CONTEXT MAKES ANY SENSE. there is no slippery slope, folks, unless you remove from the law and its invocation the existence of thinking human beings. all jokes about big government to the contrary, that's absurd
One thing I have found time and time again: It is very easy to determine whether or not a law will be abused. Simply look at the people who are worried about what will happen, ask what they're worried about, and then listen to the responses from the proponents. When the responses include such phrases as "this will not happen" "it's impossible" "that's absurd" and the like, the law will be abused in exactly the way being described.
To see too many examples from my own lifetime, you only need to look at copyright law. Laws can now be copyrighted by the writers, and legal battles waged so that the laws can be even be posted online so that everybody can see the laws they are subjected to (see: building codes for various areas around the country, such as Oregon). People working legally within their own country can be held prisoner should they visit another country (see Dmitry Slyarov). People in other countries being investigated in their own country for violating a law that only exists in the US (see DVD Jon).
I have seen any number of people worried about the laws our government enacts, and the way in which it enforces those laws. I have seen them say "Wait! Bad idea! Abuse runs rampant with this!", and be told "Don't worry. Won't happen. You're being overly paranoid." Every time that has been the response, I have later seen that law get abused in just that way. And here you are, telling me (and others) not to worry, we're being paranoid, it won't happen. You'll pardon me if, based on past observation, I am somewhat skeptical of your claim.
If you want to calm us down, and keep us from worrying, it's actually quite easy: Get limits put in the bill. For instance, this would help: "If the President uses the power granted by this law, then a vote of confidence is to be held in both houses of Congress within 48 hours. If the vote of confidence does not pass with at least a 2/3 majority of all members of the houses (not just those who attend), the President is immediately removed from office, with his successor, the Vice President, to take his place. In addition, the order to shut down the Internet will be rescinded immediately on completion of the vote." Put that in, and I'll be okay with this bill passing. The people in charge will be unwilling to use this power except under conditions that would actually require its use. Your response goes from "That's absurd" to "Thanks to this provision, we can ensure that it will only be used when absolutely necessary." Anything less than that sort of response, and I'm nervous.
Quite frankly, you should be nervous too. If you're not, you haven't paid enough attention to how power gets abused.