The hate is strong in the guy in the second video.
Here's why people hate Halo: It's main character is the distillation of the Space Marine type, in that he has no character, no defining traits other than being a great soldier, no history, and barely says ANYTHING during the entire game. In short, he's everything wrong with the FPS genre, where having your protagonist be a faceless, nameless, ageless, genderless, and voiceless entity is the norm, not the exception.
I'd also wager it has a lot to do with the fact that Halo is the game that really started bringing people into gaming that the old school really didn't want to associate with, namely "Jocks" and "Popular" people, the very people who ostracized us throughout our early lives for being gamers. Gaming was our bastion for a long time, our place to be accepted and our place to be ourselves, and some of us simply don't want to share that with people who were our enemies for so long. It doesn't help that we are seeing gaming as a whole shift to accommodate these newcomers and completely disregard the desires of the people who supported it for so long.