haven't figured out how to put a stop to obvious injustice such as this
Actually, we have. It's called jury nullification. This jury did not want to nullify; 12 ordinary people agreed to support this law. This is as fair as it gets.
They might not have even realized they could choose not to support the law, with impunity. Jurors are often given demands like "you are bound by the oath that you took at the beginning of the trial to follow the instructions that I give you, even if you personally disagree with them" that lack any constitutional basis, and the judiciary does its utmost to prevent jurors from even hearing that nullification is possible (much less any arguments in favor).
The judiciary behaves as though those people are very rare (otherwise this wouldn't be so drastically censored), and they're probably right about that. Voir dire filters out many of the well educated, and I wouldn't expect many of the other jurors to figure out from scratch "hey, if I refuse to convict, they can't actually do anything to me" or bet their freedom on that. I doubt I would have before I read about it....
Seems like many people do their best to get out of jury duty, and the ones that are willing can expect to be cut for being conscientious. The balance is tilted against the existence of an activist jury in any but the cases of the wealthy and famous. Those might manage to jolt some life into an otherwise orderly farce. Not that these jolts are positive, just unusually vigorous. Democracy is participation, Orwell might as well have retorted, some get to participate more than others.
Actually, we have. It's called jury nullification. This jury did not want to nullify; 12 ordinary people agreed to support this law. This is as fair as it gets.
It is a dumb law, though, in my opinion.