Since I am up at an unreasonable hour and actually conscious. . . Essay?
Despite all the racism essays floating around, this is not inspired by them. It actually goes back to a thread I spotted after Joshua raped Dean a little then Dean told someone that he got beaten up by a demon. Allow me to emphasize: Dean called Joshua a demon. Now, whenever Joshua has to face the eternal question of what he is, he is always explicit in the fact that he is a human. . . With some bonuses, ahem. Even if he doesn't state it, Joshua always identifies as a human! If all of his powers and everything he has done was shoved in his face, Joshua would still claim he was human albeit not a very good one.
Now, Joshua has some decent logic and reasons behind this. He was born human, first of all. He is the youngest child of the Christopher family and there was nothing special about him. Joshua only developed his powers as an apostle later on which made him sick. Then, he took the horns of a demon which only made him worse. So, if Joshua really was a demon or an "angel", then why does being either of those make him worse off? Because he is a human! Then, the Sinners family had some "racism" issues. Namely, Genai and Rizelle didn't like Joshua, because he was a human but could order them around. Genai also degrades Fiore when he gets upset. It's not a prominent feature, but there is definitely a marked division between the demons and those who aren't among the Sinners and affiliates. So, Joshua is definitely on the human side which has been made explicit to him.
Then there is the simple fact that Joshua knows from experience that he's not a demon or an "angel". Joshua has interacted with a lot of demons in canon-And by interact, I mean, he slaughtered most of them. He can understand part of where they are coming from since he is under Pandaemonium's influence too, but he also retains some definition of self apart from the hive mind. So, he knows they are an entirely different breed from him. Joshua has some pride in that fact. Since camp, Joshua has also picked up some massive hate for demons. He had a few bad run-ins with the kind as well as, you know, Chrno, so he definitely loathes them all aside from the Sinners. On the other side of the coin, Joshua has met angels in camp. He can tell that he is definitely outclassed by them, so he lowers his head on that point as he is not that stupid. Yes, Joshua is an apostle, but check the Bible-The original apostles were of human origin and charged to spread a divine message by Christ. Joshua just happens to have a different means of spreading the "message" he has.
However, Joshua doesn't care at all for the people he is going to kill! He could care less for the rest of humanity aside from his sister. As a human, he should have some morality or conscience that prevents him from doing this, should he not? In a world where war and genocide exists, Joshua hasn't fallen that far from the tree in his mind though. So, he has a different means of going about it, but it doesn't change the fact that he's not the only one who has killed another, even in large numbers. He even abides by the rules in a way. Joshua is human, so he knows that he will get his in the end-He just doesn't care.
Ironically, in some ways, Joshua understands himself as set apart from humanity though. He is human, but he is also another breed altogether. What others take for granted, Joshua has no understanding of whatsoever. He can look at his actions, seeing them as right or wrong, but he doesn't do something because it's wrong. He doesn't do it because it serves no purpose to him at all. Joshua plays at understanding feelings, like love, too. He says he loves his sister, but he is devoted to and obsessed with her in reality. So, while Joshua isn't exactly human in his mind for less obvious reasons, he doesn't really feel the need to define himself as something completely different as he is and will be the only one of his kind.