Kotaku's point - or, more of, Stephen Totilo, who wrote the article - essentially says that the ratings should be flipped: while there is killing in Halo CEA (it's not glorified, but it is tamer than what we've been exposed to in the 10 years since the game's initial release), Batman's style of flourish fist-fighting is portrayed in more extensively brutal fight sequences, what with bone-crushing attacks, and intense one-on-one combat between The Bats and the various goons.
Others were quick to point out a simple fact: you kill in Halo, you only subdue in Batman. Makes sense, right?
Gander at other franchises in the past 20 years of gaming, and watch each new entry gain a higher level of ratings on ESRB. A prime example would be The Legend of Zelda. When the ESRB was established, the first game in the franchise to be rated by the firm was Ocarina of Time, which garnished an E rating. Fast-forward a bit to Twilight Princess' release, which was the first game in the series to earn a T rating, and the only one to do so since. Beyond that game, only three other games in the franchise have earned an E 10+ rating: Spirit Tracks, Ocarina of Time 3D, and Skyward Sword.