To be very clear, I entirely agree that it is perfectly ethical for an investigative journalist to encourage a source to whistleblow crimes or information in the public interest.

I also believe that Assange went above and beyond "encouraging" to participating in, and committing of his own accord, crimes intended to either cover tracks or that gained unauthorized access to further information (whose criminality nor public interest was not known).

Cracking or attempting to crack passwords of uninvolved third parties in order to get access to or coverup your unauthorized access to information is unethical at least, illegal at worst, no more than it would be for me to clone your ID card to gain access to your employer.