This I believe.
My own dearly departed cat was fiercely loyal to me. Once, my sister and I were bickering a little, and when she walked past kitty, he took a swipe at her leg for no apparent reason. Kitty wasn't aggressive towards people at all, so this move caught both of us by surprise. I think he was making his point that he was on Team Jeff and she'd better watch her step. At other times, he faced off with big dogs in an effort to protect me when he could have easily hidden under a nearby car. I have no doubt he'd have killed and died for me had the opportunity ever arisen. And if he had perceived a threat to me, and unleashing a bioweapon against my enemies was within his power, he'd have done it without a second thought.
Man, he was a great cat. Even all these years later, I still miss my little buddy sometimes.
I'm sure someone has already written a science fiction story in which cats are in fact evil aliens just waiting for the command to destroy us all.
I think the owner of this forum has written something along those lines.