I hate that this is necessary but I feel it must be said.
To me, the lowest level of respect for a person that every single human being is entitled to is being called a human being. And that means they have full autonomy of their mind and body, for they can and should be held accountable for.
The second you dehumanize a person, you take away their accountability. Monsters have no thought process, they hurt and cause harm because they don’t and can’t know any better, but humans know when you hurt someone you are going to be held accountable for it. Or they learn to be responsible for what they do.
When you take away a person’s most basic human respect, in this aspect, you tell them this abhorrent nature is to be expected of them. Telling them “you’re a monster, it’s what you do. You cause ruin and it’s impossible for you to change.” You strip them of the very mindset that they, themselves, and us as well, can hold them responsible for the things they say and do.
I feel like this is what @markiplier was trying to say. Either way, this is my take on what he said.