Humans. Can't live with them, can't shoot them.
They are all essentially the same, with slight variations. One can see that they are all basically the same creature just by looking at them.
They can be easily divided into two categories: the thinkers and the provers. The thinkers are those who think, or at least claim to think; that is all you need for them to belong in this category.
The provers are those who prove that they think, for example by succeeding in society and the like. You don't really need to be a thinker if you can do this.
The thinkers are the worst.
Although they pretend to be thinkers, in reality they are provers. They are essentially the same as the provers, but with a different approach.