If you don't know why Code of Honor is offensive, I can't help you.
Likely you couldn't. I visited this site for years prior to beginning to post, and read various opinions (other sites too) as to why CoH is considered "racist." From what I've read ...
I don't see the culture depicted as tribal.
I don't see the culture depicted as being specifically African. Architecture and clothing are middle-eastern.
I don't see the society depicted as being primitive or simple, Troi describes it as a highly structured society.
I don't think tapping sticks together is racist.
While they do have dueling (as do the Vulcans), I don't feel this makes them savages.
We've seen other episodes where all the guest star actors and extras were of a single race (but not black). While a mixture of races were sometimes cast as a planet's inhabitants, this was not the standard.
I don't see them as backwards. While not as technologically advanced as the 24th century Federation, they were able to beam to and from the Enterprise. From Picard wrestling a Ligonian at Starfleet Academy, it's possible they have warp drive. The fact Starfleet allows contact also suggests they have warp drive.
Lutan didn't kidnapped Yar owing to
Black men want White woman, he kidnapped her as part of a plan to kill his wife.
The story makes this clear.
I do think it was good idea to cast non-white actors as leaders and citizens, if anything this should have been done more often. Black, East-asian, Arab, others.
While the main cast isn't all white, you can't say the same about
the majority of guest roles. I'm not suggesting quotas, but come on mix it up some.