I'm just going to share an experience by saying that I have a younger brother (not namedropping anything) and I have regarded him in most of my life in a neutral-leaning-negative light, he's annoying sure, but he's not like really shit, or at least, I had until he started calling me a "black person", "blackie", and "monkey" (which I'm pretty sure is often compared with to black people in a really dehumanizing light) just to get a rise out of me, which first of all, is not accurate at all (I'm Asian), and second, it sounds like he was being genuinely racist against Africans just to piss me the hell off, "at the very least he isn't saying slurs" I thought to myself, months later, he recently started calling me the fucking N-word, really, really casually, just to piss me the fuck off, I don't know if he's being genuinely racist or just wanting to get a reaction out of me (I'm 75% sure it's the latter), but even then, using slurs just to get a reaction out of someone is tasteless at best, and outright derogatory at worst.
I'm just curious if anyone else has experienced the same thing as me.
One of my oldest friends had caught a stupid habit in high school. He and his friends, the pastiest kids you can find in all of west Asia, and they were referring to each other and sometimes others as "black" or the n-word. They grew out of it, thank fuck for that, but it was a weird period.
This specific thing you're suffering I've never seen, but kids doing dumb shit to get a rise out of older siblings is a tale as old as time, so is teens being edgy and "non-conforming." The escalation that you've noticed is clearly because the little dickhead is prodding your sensitive spots leaning on what works. Sometimes a good conversation, getting real and all that makes them stop, sometimes the kid doesn't stop until they grow out of it.