It's not a "rationalization" to question the principle that a crime must involve harm to someone. Your example of speeding could possibly be an exception as in the cases of "justified" dangerous behavior that has a demonstrable higher than average probability of resulting in injury. Even that's a very slippery slope (Is consuming cannabis or alcohol a demonstrable danger?). And, as the book I referenced above makes the point, with the volume of laws on the books and their sometimes almost arcane detail, it's likely almost everyone violates the law, even at the felony level, on a regular basis... and is thus subject to arrest and prosecution should, for any reason at all, the government decide to "target" a particular person. Thus the Stalin "secret police" Lavrentiy Beria quote "Show me the man, I'll show you the crime". I.e. Everyone is guilty of something, and if you want someone "out of the way" we will be able to arrest and prosecute them for something to get that job done."
I contend that the NFA (and the GCA 1968) is a preposterous violation of individual liberty that is protected by the constitution. Maybe, maybe, someone wants to argue about where "the line" "should" be drawn... but it sure as hell can't be justified at "suppressors". And I'd argue it can't be drawn at "automatic", nor the length or a barrel nor overall length either. Absurd. "Intolerable Acts".
I'd hope that in the case we are discussing that jury nullification could have been in effect, but apparently it wasn't a jury trial, but decided by a judge. There isn't that much difference between the guys in the black robes and the guys who bring the people before the black robes. Whatever Pick's motives or intentions were or weren't, he never harmed anyone, and shouldn't lose his freedom for simply possessing some item that someone somewhere thinks he isn't entitled to possess either at all, or unless he jumps through hoops and pays them money. How can these people have even the slightest sense of wonder about why people disrespect the law?