How is my epistemology confused? SOPA gives the government the ability to legally shut down web sites. That's what the law says. We can know that because we can read the law. Generally, if you read something, you can figure out what it says. That's far firmer epistemic ground than speculating about, as you call it, the contents of someone else's brain.
We don't have a time machine, so neither of us can actually know the effect. So how are you figuring it out? Legislation by itself has no effect – it's just a piece of paper – the enforcement is what counts. And how a law is enforced is based on its intent (its real intent, which is not necessarily the justification given to the public).
So you're figuring out its "effect" based on the inferred intent, then turning around and saying that the authors' intent is unknowable.
I'm not inferring intent at all, I'm saying that a law that says "the government can delete your domain from DNS" gives the government the power to delete your domain from DNS. How, when, and where they will use that power, I don't know.
Also, laws aren't always used the way they were originally intended, because laws tend to outlive the people who wrote them. But how, when, whether the law is ever actually used is already very much beside the point. The point is that the government would have the ability to do a certain thing, not that they actually would or wouldn't in any given scenario.
