I think it's so universally hated just because it keeps contradicting itself. Star Trek fans can normally accept things as long as they are somewhat established in the Star Trek universe. When an episode goes against what they've established then it makes it hard for the fans to accept it. It's one thing for continuity errors going from season one episodes to season five or whatever, but to have them happen in a single episode makes it hard to follow.
What established lore in Star Trek did it contradict?