AFAIK there is no proof that the bugs are the ones that the prophecy is talking about. Considering their aggressive behavior if they are the 'star gods' (& I use the term with a pinch of salt) that visited Kilrah eons ago, they probably would've butchered everyone there.
Kn'thrack would've been written by a cat as it's doubtful that a bug would've known the word, it's meaning or how to spell it. The Kilrathi probably wrote it because the bugs used the fleet plasma cannon to destroy their fleet. If the new enemy has such a devastating weapon what chance do the cats stand? They've already been beaten by the Terrans so the arrival of this new race, which is so easily annihilating them makes it logical to assume that Kn'Thrack is occurring. "Kn'thrack, or "void," would occur if the Kilrathi were defeated by unworthy opponents and the star gods returned to annihilate the race without honor." - WCP manual.
So I told them straight - we'll decide how to spend our defence budget, not them!
How did our allies take that?