Its about A Mate and his players, if I said me and my players I made a mistake and apologize, and my mate knows his group well enough that their are several ways that can justify in-game racism against fantasy races or cultures that doesn't also serve as a rationale to justify real-world racism against actual races or cultures?Except that this is very specifically an example that, over the past several years, has been called-out as seriously problematic to the extent that it's been largely abandoned and overwritten in official publications.
What purpose does it serve to include these fantasy-racism elements in your campaign? In particular, how does this weird elf-thief prejudice lead to any interesting character developments in the story you and your players are telling that is not also deeply problematic? And is there really any way that you can justify in-game racism against fantasy races or cultures that doesn't also serve as a rationale to justify real-world racism against actual races or cultures?
But I will admit that he's the only GM I know or have ever known that would be guaranteed to succeed at justifying in-game racism against fantasy races or cultures that doesn't also serve as a rationale to justify real-world racism against actual races or cultures, other GM's?, not any that I know