OK, but suppose you're trying to frame them for bank fraud. Coming up with incriminating data is a lot trickier than just making it look like they have something.
Refusing to decrypt under this law will be the crime. It's not proof against you in the original charge. So you won't get them for bank fraud anyway, and then it might as well have been child porn (or a stash of stolen credit card number or compromised online banking accounts etc)
