Intense (yea, homicidal) hatred for people one cannot possible have known well, is known as "schizoaffective" (schizo / detached from reality plus "affective" / emotional effect). 

Ideas-of-reference (what the principle experiences as Truths of transcendent importance) drive schizoaffective rage. Typically such types externalize personal feelings of humiliation, inadequacy, inferiority projecting some of their own bad qualities onto others. Paranoia ensues when one comes to believe that others are conspiring against them purposefully. 

That's why it's often regarded as "paranoid/schizophrenia".  

The ethnic or ideological supremacist convinces himself that others are conspiring against him and all others "like him", ruminating ideas-of-reference frequently aided by militant, fanatical writings/media. 

That formula holds true for anything from anarchists Sacco and Vanzetti, ethno-supremacists, muzz-Twelvers/Wahabi terrorists - countless others for whom ideological avenues were merely the street where the out-of-control car of their mind careened into as it hurtled toward violence.

 IOW, if the specific political/ideological events had not attracted them as a good reason to slaughter innocent people, they would have readily found another. 

One of the first principles of human motivation is that people will inevitably find what they are looking for - which is to say, if a person has a strong enough need to solve a psychological issue through violence, they will somehow "discover" a reason. 

"Unconscious material seeps upward like water penetrating a  structure from below." - CG Jung  

"Those who absolutely deny any effect upon them by their unconscious material are the ones most likely to be completely consumed by it." - CG Jung