Real answer: It’s not that knowledge is itself evil. It’s that by obtaining the knowledge of good and evil, mankind was responsible for its actions.

The idea is that animals aren’t capable of being good or evil because they have no knowledge of the concept. Whereas humanity’s knowledge and understanding means we’re aware of the morality of our actions.

To put it in a more contemporary, non-religous context - you can’t blame or judge invasive Kudzu or Bark Beeltes for the environmental damage they cause because they aren’t aware of their impact. Humans are aware, and should be held to account for their actions.