I've commented on this before, for the most part I don't give a crap, thematically The Empire and it's "Nazi analogy" was supposed to be about human supremacy, being anti-alien more than about anything ethnic within humanity. An Alien showing up in imperial uniform would be the big issue as opposed to a black guy. The EU defined things where The Empire went out conquering and subverting planets and then conscripting large portions of the inhabitants into the military and then sending them out to attack other planets (getting the dangerous guys away from home, and keeping them under control as they mix up the conscripts). The old "Tie Fighter" strategy guide (I think it was) had some short fiction explaining that the main character was supposed to be conscripted from one of the world's conquered by The Empire and one of his friends had become a Storm Trooper. Likewise while it was a matter of bad writing, Luke was both wondering in the first movie about fighting with the Rebellion, and wanting to head off to "The Academy" to train and get off Tatooine, which at least implies there is some recruitment going on, and as we've already seen The Empire has no problem dealing with people based on skin color as it was more than willing to subvert Lando as opposed to just flat out killing everyone and taking over Cloud City so I see no reason why if someone of color wanted to join their military there would be a remote issue... now if a Twi'lek wanted to do it, that might be a problem.
Of course the reason why I say "for the most part" is because one of the first things they did when announcing this new series as to toss literally everything outside of the movies into the rubbish bin, which means that by definition all Storm Troopers are going to be clones of Jango Fett, which of course means you can't have a black dude, or a white dude, or anyone who isn't specifically Jango Fett who is a Maori (as the article points out) inside one of these armor suits.
Now, common sense dictates that perhaps some things from the EU survived in some form, and that yeah, The Empire is recruiting humans. That would make sense on a lot of levels, including why the Storm Troopers in the original trilogy were incompetent compared to the clones from the prequel, not all of them had some of the skills of the universe's greatest mercenary and bounty hunter. Likewise as The Empire cements it's power and pursues an increasingly anti-alien agenda it's quite possible they might not want clone troopers to keep being manufactured as they are the result of alien science (created by "The Cloners"). The storm troopers in many cases being a bunch of conscripts with fancy armor and minimal training would explain a lot, while still acknowledging there is a core of very dangerous clones out there as well.
Of course I think this trailer was race baiting to get attention, which worked, as a huge song and dance was made about "abolishing everything not from the movies" which would imply all Storm Troopers being clones, and then the first thing they do is show a black dude in Storm Trooper armor which makes zero sense given previous statements. Sure with context and embellishment this could have been explained and worked around, but when people complain all they are getting is a "get used to it" which is kind of inflammatory, and is probably intended to be so it will generate more conversation.
I mean sure the guy could be disguised as a Storm Trooper, or even an actual Storm Trooper recruited from some planet or other The Empire conquered or opened a recruitment office on, which is something they could specify since they have certainly brought this on themselves by dogmatically claiming only the previous movies are canon, and it would probably actually help to smooth some things over above and beyond this issue itself.
Basically I think the idea was to start a race war for publicity, and it's being treated that way in response given that goal. In reality I think a lot of Star Wars fans see this as being similar to if we saw a zombie shambling along in Storm Trooper armor which for these purposes would be the same thing, as it would be implying something from the EU happened (Death Troopers series) which granted is more ridiculous than non-clone Storm Troopers due to recruitment and conscription, but the point is that both have been declared equally non-canon.