True, but it was a major theme over all.
But I also doubt Terra Formers themes is about racism at all, and more about people fighting monsters. Which goes back to the question of why he even designed the Cockroaches like that at all?
I know he probably didn't mean to be offensive, but maybe you know, you could have an editor or some one say. (Dude this might be a little racist,) I mean that is why we have editors and beta readers for EVERYTHING cut some stuff out, is it offensive? Does it need to look/ be like that. If no, then change/ cut that shit.
It might sound like some petty work and what not, but as long as it's not plot crucial or important to the character then you can change it. (I fail to see the point of the Cockroaches looking vaguely African American have anything to do with the plot,)
Then again, this is why we have editors, because trust me. Rarely is your first draft your best draft and getting other peoples opinions might help you catch something that doesn't make sense plot wise or could be offensive and change it.
When the author of Naruto is more self aware and conscious of the different races around the world and portrays them better, there really isn't an excuse for it.