I know there are readers that are so used to any native characters (African, American Indians, etc.) speak in stilted language ("Him Panther - Big Chief these parts!"), that you can't imagine that those people don't actually speak that way.
This just proves to me that he doesn't get it.
Transliteration is fine for contemporary works. I use different slang when I speak Spanish than when I do English because the meanings don't carry across. But this is modern slang in modern times.
By putting modern slang into the mouths of historic people you draw the reader out of the moment. The key to any good story is to draw the read
into the story by using dialogue and setting. You want the reader to feel that the story is real and they are observing it. By having ancient Africans use modern slang, he basically yelled "HEY THIS IS NOT REAL," and violently yanked readers away from the fantasy of the story.
There's no need to go the other extreme either and make the language stilted. All he needed to do was use real sentences and real definitions. If he wanted to get the meaning of "We'll kick your butts" across, he could have said, "We will defeat you."
Someone is likely to counter that saying it my way wouldn't sound as "natural." That's the exact point. These are people who lived hundreds of years ago or live in totally different countries, who had totally different sentence structure and colloquialisms. By having their speech sound unnatural to us, but not in modern slang, it reinforces the alien nature of these people. They
are different from us therefore they
should sound different than us.
And that draws the reader
further into the fantasy of the story.
My personally belief, and it could be entirely untrue, is that Hudlin doesnt get the idea of fantasy/adventure writing. Everything else, that I know of, that hes wrote dealt with more modern, real world settings. The rules for that type of story dont apply the same to comics.