Conspiring a felony is not free speech. He received top secret material from “Chelsea”, urged him to commit more crimes and helped to break into DoD secret computer systems.
This is why they put Bradley into solitary for 2 weeks and put the screws to him.
The correct defense is that Assange is not a US citizen, and has never been on US soil. US laws do not apply to him.
And if they do, then the laws of the EU, and of China, and of Saudi Arabia apply to American citizens, even if they’ve never visited those countries.