Reddit explains it quite well and also offers papers for additional inside about this topic:
https://www.reddit.com/r/kpopnoir/comments/1uevz70/song_of_the_wasteland_and_how_insensitive_it_is/
Once again
The whole thing is tonedeaf af as fuck. It leans into racist tropes like the slave/master dynamic and the white savior narrative. Same as trying to romanticize a Nazi/Jewish relationship or an Imperial Japanese soldier/comfort woman relationship. The history behind those dynamics makes them VERY problematic to treat as romance.
Also, the enslaved characters only exist to thank a wealthy blue eyed white protagonist for "saving" them.
Ezra's design is weird as hell, no tribe, short hair, blue eyes to tick European beauty, amber skin for exoticism, pearls in hair as a "culture element"... He's a walking fetish.
It's a story that uses the horrors of slavery as a backdrop for a romance.

Like I srsly don't understand what's racist in this, nobody said the n word there or anything like that..