(Obviously you do need to use it sometimes, in an academic context for example. It's a tricky one.)
I'm not sure if that causes the word to be avoided in academic writing, I suppose largely yes (for its lack of any well-defined meaning) with some exceptions (probably by those who agree with the propaganda surrounding the word).
The only way to meaningfully use the term "terror(ism/ist)" in academic writing is to exactly define at the start of the paper exactly what you mean and also what you don't mean by "terror(ism/ist)". This may attract knee-jerks of "that's not what it really means/etc", thereby detracting from the main point of the paper.
The other problem is, that even if you nail down the definition, it's still contested because it's a very loaded term no matter how you turn it. The academic goal is objective description, not pointing out good guys and bad guys.
Once you get past that, next problem arises, which is that International Relations just isn't always a hard science (just like History is not). So even if you got a clear definition, and it's accepted that both parties are equally bad, it can still be quite fuzzy whether it's "really" terrorism, because the one guy did this, and the other troops such, but then the guerillas, however it was the rich families that something or other, and Ted supported George, while Bill's family lived on the land for generations, blah blah bla etc. I really suck at history, it's just confusing.
All in all it's just more accurate to describe who did what, and if you want to describe something "terrorism"-ish, it's better to just describe reasons behind the attacks, the psychological goals, and psychological effects certain attacks had on the population, etc. Basically just say what you mean (even if they're theories) and state the facts, but avoid the loaded term.
Don't use that word. It's barely even a word any more, its become one of those weaponized magic symbols used for mind control. See also "freedom", "globalization", "sharing", "choice" and so on.
Instead, you can just use words like "murder", "destruction of infrastructure" and the like.