Human are more intelligent than say horses, because humans understand horses better than horses understand humans.
Whenever an intelligent species come in contact with an lesser intelligent one, and both are competing for same resources, it leads to extermination of lesser intelligent one. If lesser intelligent species is non-competing but useful, then gets consumed or gets subjugated for repeated consumption.
For same reasons, humans exterminated other Homo species like Homoerectus, Denisovans, Neanderthals and enslaved Cows, Sheep and Chickens.
Considering our own history, it is not irrational to fear AGI or Aliens.