The warning, "If you attack me, I'll retaliate" is not normally considered to be blackmail in the same way that "Do what I say or else..." is. Assange and Wikileaks may be guilty of the former but I am not aware of any statements that would make them guilty of the latter.
As for cyber terrorism, Wikileaks itself has been the victim and many people consider it likely that the US Government is at least one of the perpetrators. Wikileaks is also the victim of behind-the-scenes arm-bending by the US Government - one wonders what sort of blackmail threats were used to cut off Wikileaks financially. I for one hope some of those conversations have been recorded.
The current US administration seems to be guilty of petulance and abuse of power - if the republicans were smart, they would exploit that rather than indicate they would be even worse. I'm not just talking about Wikileaks but other affairs such as the BP Oil debacle. For instance, BP agreed to set up a 20+ billion dollar fund for cleanup and compensation and then a couple of months later they are cited with others in a law suit seeking unlimited damages. The only winners in that will be the lawyers - remind me, what was the President's profession again...
From now on, no oil company will go anywhere near deep water drilling - the US Government won't be able to give licenses away in the future - that's not smart government and I would certainly like to hear as many leaks as possible on the way that's been handled. Plenty of warnings will have been given about creating long-term problems for short-term political gain - I'm sure those warnings would make fascinating reading.
In court, witnesses are required to tell the whole truth in order to allow a jury to come to the right decision. If politicians are allowed to bury the truth because it is embarrassing, how is the public expected to come to the right decision when choosing how to vote?