I note that what freaked them out was a professor who pointed out that, taking account of the classical definition of "terrorism" as "the threat of force against civilians to achieve political goals", there were US activities in such places as Vietnam and Nicaragua which fell within this definition

And surely noone could disagree with that. I mean, some might argue that, in the historical circumstances, there was justification for the terrorism, but that is another matter entirely - and one which does not enter into the definition of terrorism. (For, after all, that is a claim which is commonly made by organisations carrying out terrorist actions.)