"...'terror' (i.e. they're doing it to frighten us, because they're beastly, or something)...?"
Part of the process of "othering" requires the removal of cause and effect. "Terror" has no cause. it cannot be presented as an effect because that implies causation and that might lead us, for example, to join the dots and question our leaders heinous policies worldwide.
Rather there is no "cause" because outside our social world all is dark and irrational and in the "others" who live there such "evil" is doubtless innate. As such they are not truly human nor civilised like us & can therefore be killed with impunity: thus the circle goes on.
-Its a handy self reinforcing mechanism of imperialist racism.