let’s talk about flaws
namely, the flaws of mccoy
he is, at the very least, comfortable using xenophobic and racist terminology. hobgoblin, as he uses it in aos, is clearly derogatory. he isn’t being affectionate with spock when he says it. he’s angry, and he’s lashing out.
so he describes spock with a word he knows is unkind. spock isn’t human (and, presumably in mccoy’s mind, isn’t behaving as a human would), so leonard has to use a term for someone who isn’t human. thus the xenophobia.
in tos (and as ambassador spock in aos), spock is played by jewish man leonard nimoy. gene roddenberry, a man nimoy himself described as antisemitic, would have known nimoy was jewish (not least because nimoy drew on his jewish heritage to flesh vulcans out- the iconic vulcan salute came from an experience during nimoy’s childhood in a synagogue). the original design for vulcans even included horns- something that, to put on a jewish man, would absolutely invoke an antisemitic trope: the idea that jewish people are demons/(hob)goblins/inhuman.
the writers- esp at the time of tos, which established the use of the term- had to be aware of this when they put it in.
they knew they were going to make a southern white man call a jewish man a derogatory term.
bones’ being southern matters because writers use a lot of shorthand. one trait signals a bunch of others. and you may not want to hear this, but to a lot of people, the first thing we think of when we’re introduced to a white southern man is racism.
and to have that white southern man use a nasty epithet to describe an alien, jewish character (repeatedly, in the case of tos) as a hobgoblin is of course going to resonate with audiences as more than the simple poking of a prickly friend. particularly when you remember that bones and spock aren’t friends yet when bones says it in aos.
that doesn’t mean we can’t enjoy him as a character or relate to him. but we do need to be critical about who we defend and how we defend them.
tl;dr mccoy is far from a sweet, unproblematic boy. he was deliberately written the way he is, and as uncomfortable as that might make fandom, that means that when he calls spock a racial epithet, we need to take note.
as a southern jew, I can say with absolute certainty that the way mccoy is designed is very typical of southern white men. white people here especially are very comfortable using racist and antisemitic terminology and don’t much care if it offends you, if you get offended you’re just taking it the wrong way.