I didn’t. At the time. But now that you make this interesting comment - I can see why someone would see that in the scene.
In general, I am wary of any trope involving white people saving masses of helpless blacks or dark-skinned people. Obviously, it reinforces all the cultural ideology and stereotypes around white man’s burden and “humanitarian” imperialism.
And in the Game of Thrones scene you refer to, it can’t be ignored that the slave master and citizens of Astapor speak in a fictional tongue that has a distinctly Middle Eastern / Arab sound to it. Even if it’s entirely fictional (on an interesting note, I learnt on Cast of Thrones podcast that a linguistic expert was hired specifically to create fictional languages in Game of Thrones!). Reinforces all the myths about Arabs being inherently tyrannical or submissive to tyranny.
So maybe those people have a point. Obviously I don’t think the writers of the TV series intended for it to be like that. But that’s the whole point of implicit racism - that it’s implicit…so that doesn’t excuse them. But I don’t know what definite conclusions I’d draw from it. I’d have to think about it a bit more, maybe. I’m not exactly a film critic or anything =P