How to deal with racism as a Catholic

To start, I'm not the one experiencing any racism of any kind. In fact, it's my younger brother who's recently turned into a teenager that makes a LOT of racist comments or "jokes" (my older sibling also does it, but I don't think I can convince him). He thinks they're funny and it actually disgusts me, it's infuriating.

Obviously, racism of any kind is sinful and discriminating, so I don't get the point of racist jokes that promotes seeing a different race as inferior.

I repeatedly say it's wrong and such, but I'd like a Catholic approach on it (such as one that touches on its sinful nature and how terrible it is for his relationship with God and in general). I don't want to belittle my brother or insult him, I'd appreciate any help dealing with this to a kid. Thank you.