The only people who disagree with this statement are people who are simply not informed.
What you see from groups like the ACLU, EFF, Demand Progress, etc. is opposition to the specific language in CISPA, not opposition to the concept of a cybersecurity bill in general. They did not oppose the Senate bill last year for instance.
Actually, that's not only a fairly weakly implied argumentum ad populum, as it doesn't actually argue that the number of ignorant people are small or the number of non-ignorant people are large (though the use of "only" might imply that.)
"The only people who disagree with this statement are people who are simply not informed" is more directly argumentum ad hominem, and, particularly, abusive ad hominem.
Its also, simultaneously, petitio principii since claiming that disagreement with an argument can only be due to ignorance to support an argument is equivalent to claiming that the argument is true to support the argument.
I agree with your points, but I set out to mention just one logical error, and Argumentum ad populum seemed most apt as a single example.
The argument that only a minority of misinformed people hold a particular view is a negative version of Argument ad populum. Apart from that, I agree with your analysis.
It's easy to argue about logical fallacies because anyone can look them up on Wikipedia or Less Wrong.
It is harder to make a substantive case against the need for a cybersecurity bill because to do that, one would have to actually know what one is talking about.
Here is an example of the sort of distortion that the current legal environment is causing:
I hope you will consider the idea that if companies feel forced into going to lawyers for network security advice, the system might benefit from a bit of tweaking.
Oh, well, since you put together such a persuasive argument.