Humans are humans, whether you like them or not.
The bad thing about Nazis is they disagree. Feel free to be more like Nazis? I'd prefer to be different. Still human, but you know, acknowledging my fellow humans as such.
To ignore this fact is to lay claim to the idea that you could never end up in a situation where you're treating people as subhumans. To call any human as subhuman is obviously antithetical to making that claim.