Whenever one wants to justify violence against any individual and/or a group of individuals, they invariably seek to dehumanize them (usually in the most callous, vicious, and vile and degrading language available)!
Take for example, the justification of slave-dealers and their supporters, who convinced themselves (in order to justify themselves) that blacks were property and were not actually human at all. And so, no one else has the right to tell them what they can or cannot do with their own property.
So ... if your 'religious' belief is that a 'slave' [one of the nicer terms used] is a person, then don't own one: That is your choice! Just don't shove your morality down my throat!