Mr. Sonne went out of his way to purchase specific chemicals that are integral components in bomb-making.
So what? Not illegal to purchase those components if you aren't making a bomb. In fact, it isn't even illegal to buy those things even if you're "thinking about" making a bomb. Possessing these things isn't a crime unless he actually builds a bomb. He didn't build a bomb, never had any intention of building a bomb, and the cops KNEW full-well he had no intention of building a bomb.
So why the charges, if not to silence a critic?
He went out of his way to express his intentions to "test security" at the G-20 summit.
Not illegal. Ever heard of "Freedom of Speech?"
Security took notice of those activities (which he apparently assumed they wouldn't), and they responded as if he posed a threat to bomb the G-20 summit (which was exactly what he tried to make it look like he was thinking of doing).
More like they saw that a guy who'd been criticizing them publicly for ineffective security regimens and saw an opportunity to tarnish his reputation and chill his speech in the future by branding him a terrrorist. Even though he's been acquitted, the damage is done: In the narrow-minds of many this man is now a "terrorist" and damaged goods as a security analyst. ...All because he criticized the wrong person.
And really, how anybody can claim it is anything else than that is beyond me: Almost every advanced nation factors a defendants INTENT to commit a crime into the equation of whether they're guilty or not. In no scenario can anybody claim this guy had intent to blow anything up: He's said he never intended to, and no investigator when pressed has EVER presented evidence he intended to build a bomb. This is a "wink-and-nod" between the cops involved to strike-back at somebody who is critical of their security-theater gravy-train--nothing more.