The graphics, combat, and acting are incredible. That much is almost universally agreed upon. It's the story that made so many people throw a hissy fit.
The reasons people hate the game are:
1) They took issue with the direction of the story, which is intentionally dark and upsetting. This a very valid reason to dislike TLOU2. I personally found the plot to be a fascinating dive into the minds of the main characters, as they struggle to reconcile their anger and grief at the expense of those around them. However, that's simply my opinion. There are definitely certain scenes and character choices that will understandably turn people off. It's a grim game.
2) They see this game as some sort of political statement (which it really isn't). The entire extent of this game's "political agenda" is that a couple characters are LGBT. That's literally it.