A thread on a random episode is probably not the ideal place for this conversation, and I might not be saying anything that hasn't already been said in the actual discussions on the topic, but ...
While I can see how the role of POCs in this episode can come across as upsetting now that it's been pointed out I believe that it wasn't intended that way. On the contrary, it seems to me that Doctor Who (its modern incarnation, mind you) strives to show diversity in its cast.
I've got to admit, I'm a lot more cynical about diversity in Doctor Who than this. This might come up as pedantic, pernickety, and possibly tin-foil-hat-wearing, but .. as *diverse* as Doctor Who casting has been, I'm not sure it's been inclusive, and it most certainly hasn't been representative.
It doesn't have to be representative, of course - a small sample taken from a large population at random rarely is, after all (which is why you'll find both the highest and lowest incedences of diseases in small administrative units). But be it random chance or something else, we haven't been seeing overly much of the
by far largest ethnic minority in Britain: Asians. There are more than twice as many people of Asian (primarily Indian and Pakistani) extraction in the UK than there are black people, and yet there's been .. Rani and her family on SJA, and that's pretty much it.
This has some uncomfortable implications for me. The BBC has been quite interested in the US market for some time, and Doctor Who is a pretty big export. And the one ethnic minority that gets fair representation on Doctor Who happens to be the one that the UK and the US have in common, while the ethnic minority the US hardly has is petty much left at the wayside? Hm.
When an advertisment in the US has a diverse cast, my assumption is not that the company behind it is dedicated to social justice ... my assumption is that the company behind it is mindful of good marketing. I'm really not sure this doesn't apply here, too.