If the yeerk threat was real..
Hm, well first of all, before the Animorphs were even aware of the Yeerks, they had been around on the planet for at least 2 generations, when Visser One first went down to the planet. If Elfangor hadn't told them all about it, they would never have known until they were infested.
So, if the Yeerk threat was real, in all likelihood, we wouldn't even know to fight it, so preemptively, I suggest you all stock up on instant maple oatmeal, just in case, and perhaps become emo and never join any groups that claim to do good in the world.