"They could reasonably have expected to be charged with trespass and vandalism but to be labelled as terrorists is ludicrous"
No, it was very reasonable to expect exactly this to happen. They were offered pleas, but choose not to take these pleas. The US justice system always retaliates against defendants that are unwilling to take pleas. I'm not saying that it is morally right, but I am saying that the defendants knew this very well and willfully choose this over other options. As a result of this you now know about them.