I personally don't think they are required to know who they are, they did mistake of referring them as BTS, but I think i get more on radio stations side, kpop is not as much in their territory than us pop is and mistakes like mistaking another kpop group for BTS is bound to happen and they could have just thanked for correction and say they will get it right next time.
It was disminishing to say they are random Asian guys, i guess it could have been made in more lighthearted manner than meaning bad with it, but still disminishing. And the thing about Justin, Arianna and Taylor.. it's kinda true i guess, but it's still bit US centric view, there are lot of people in the world that know them better than those three.