Because those of us who haven't seen the Light of GRRM's good Word are lost in the Dark? HBO purists must seem like mole-people to you.
Game of thrones spoilers i guess
Spoiler:
No, because the show is fairly ridiculous at several points due to the massive leeway they get. So ridiculous that it certainly shouldnt be getting as much hype as it is outside of people looking to see boobs every 5min.
Consider the scene you just linked. How can anyones reaction be anything other than wtf? The very first scene of the show has a search party slaughtered by these guys for no reason. Now theres a huge army, and upon seeing someone from the opposing side, decides to do nothing. Wat.
Lets take a look at the Tywin arya dynamic. Lord Twyin, The past king's father in law, is unable to recognize the king's hand's daughter? Erm hmm. Clark kent isnt superman, hes wearing glasses!
How did jon snow get separated from his group on the other side of the wall? Are we to believe they just decided to abandon him? Seems competent.
Dont even get me started on Dany's arc in the second season. My god.
I havent seen the show in a year or so now, but theres a ton of other examples. This is just what i could easily remember.