Question about ethnicity slangs that I'm reading people find racist...

Hi, as some of you probably already will know, today it was revealed that the Lunar Remastered Collection will be released on the 18th of April. Under that announcement I've read a lot of comments that asked the translations were not the Working Designs ones anymore.

I'm a curious person, so I searched why those translations are so despised so I ended in a ResetEra thread where there were a bunch of screenshots of the game where some characters talked in an "ebonics" slang (new term for me, just learned it now).

Many people said that this way of adapting a script is racist, but why? If the slang exists then it's possible to use it on some of those characters that in the original Japanese script talked a bit differently than grammatically correct.

It happens always in Italian localisations where characters that speak with a strong Japanese accent in the game talk in Sicilian or other dialects, so why a "hood slang" is seen as racist in the US?