Which piece of evidence best supports the idea that dehumanization increases immoral behavior?

In between 7th of April 1994 and July 1994, Rwanda witnessed a genocide which cost about 1 million lives.

During the dehumanization, the organizers utilized the instrument of equating the Tutsis to snakes and roaches. It was an instrument they deployed in order to consistently dehumanize their victims.

Dehumanization is an act of downgrading and degrading of human beings or making humans to be equal with animals or to other non-human creatures. Dehumanization is referred by Prof. Gregory Stanton as the fourth in genocide out of ten.

Dehumanization has always been part of a genocidal government which they use to excuse their action on their target.