>>213532512
To answer seriously, people weren't mad about it back in those times because there wasn't any clear and obvious "white people bad" narrative being pushed when you saw a black character on screen like there is now mostly. Back then they weren't always perfectly morally just mary sues who were always the victims of white people, and the black villains weren't also "bad" in a sense that the only reason they are evil is due to white people corrupting them. The ambassador here is a cool character who is in league with the Persians and that is that, we don't have to worry that his presence on screen is the directors way to lecture us on our "privileged" or whatever.
Nowadays, whether or not that is the intention of a director, we have to wonder each and every time there is a nonwhite person on screen and as a result the well is thoroughly poisoned for the foreseeable future. Another example of this is Morgan Freeman literally playing God in Bruce Almighty, there were no political undertones (or overtones) to it whatsoever and so the fact that it was a black man playing God didn't matter to most people whatsoever.