In Tomb of the Cybermen, the other Doctor Who story where the Cybermen come out of their tombs and an over-the-top villainess with a funny accent has given them the means of doing it in the hope of gaining control of them as an army, the first character we see on screen is a character named Toberman.
As you can probably guess from how he's presented to us in that clip with special emphasis given to his presence, Toberman is sort of the hero in the story. He spends most of the story working in servitude to commands given to him by the other characters, with his fighting skills being his main asset - a soldier, you could say. He is able to pass into the world of the dead by being the only person strong enough to open the doors to the tomb, and when the villains cause the Cybermen to emerge, he is converted into one. The Doctor appeals to his humanity, and he turns against the Cybermen, killing them before sacrificing himself to save the Doctor.
This all sounds rather better than it actually is. Toberman may be sort of the hero of the story, but in the most racist way people still seriously defend. His characteristics are that he virtually never speaks, is subservient to the other characters, super-strong, temperamental, proud and stupid. "He was supposed to be deaf," say certain fans, waving their Target novelisations at you, "you shouldn't criticise, you should celebrate the show for having a disabled black man in it as a hero." This is a terrible argument, because his 'deafness' only exists to characterise him as having no words or ways of understanding the world of his own, and because Toberman's alleged deafness is never mentioned or so much as implied in the script or acting, ever.
Toberman doesn't just exist in a world without a means of expression, or perception, or goals or dreams or character. He even exists in a world without love. Kaftan, his boss and the person he's the closest to in the story, doesn't care about him at all except as a body. The Doctor, a hero representing love and freedom, makes his appeals but it's only to use him for his own ends himself - bonus points for making the mega-racist allegorical implication that he (and black masculinity itself) only became enslaved through his own choice! And when Toberman sacrifices himself, it isn't done out of love for anyone or anything else - Cyberconversion stripped him from all apparent emotions except for a desire to kill the Cybermen. His scene of sacrifice is painful to watch, because he's so out of it that doesn't even seem to be aware that he's making the decision to die, making it even meaningless.
Despite this, Tomb of the Cybermen is still taken seriously. Neil Gaiman said it was his favourite story, while Matt Smith famously called up Moffat in the middle of the night to squeal about how good it was after watching it. There's no other racism in Doctor Who so extreme that simply never gets commented on. Talons of Weng-Chiang, in which the only noble villain is a white man in yellowface and the Doctor joins in with the side characters in making racist jokes about him is roundly derided for the racism even as people praise the production values, the dialogue and Tom Baker showing off a bit of acting range in it. The Celestial Toymaker, which has a white man in Chinese dress as the villain and uses an older version of Eenie-meenie-miney-mo, is only even remembered for being 'that Doctor Who story with the n-word in it', and its 00s sequel goes out of its way to have a scene in which the Doctor yells at the villain for mindlessly appropriating cultures he doesn't respect. But Tomb of the Cybermen is still thought of as a highlight of Troughton's era, and everyone seems to just forget Toberman exists.
I don't think we should. We need to remember just how bad this show could get, otherwise we'll never really understand how to improve.
And the show has improved, it has gone out of its way to improve as much as it can. But in its constant nods to and references to its past, you get stories like Nightmare in Silver that reference Tomb of the Cybermen, without acknowledging the fact that the hero of the story is a really insulting stereotype of a black man with no agency of his own.
I can't say I was a huge fan of Danny Pink's character. He and Clara seemed to have little reason to want to be together and both were thoroughly shitty to each other, although for different reasons and in different ways. And then Danny crossed through the threshhold into the land of the dead, and the hammy villainess made the Cybermen come out of their tombs, and Danny got Cyberconverted, and placed against his will into the role of Toberman.
We never doubt Danny's intelligence or fundamental good nature. He owns his mistakes and makes his own decisions. Even when he lives in a world without words or emotion, his decision to sacrifice himself is made from the emotions he felt when he still had them.
It's so easy for the show to look back at its own past and pat itself on the back, indulge in the behind-the-sofa moments and the funny lines everyone loves. But it was brave of itself to risk reminding us of Toberman. And good of us to do so by spending a whole series reinventing and saving Toberman by making him a person, a human being, with his own outlook on the world and his own life, instead of the hollow shell he was. And long overdue. And imperfect. And needed.