I believe the core issue is that the new change moves dangerously close, if not crossing the line, in to forced speech and certainly moves away to the assumption of positive intent. This entire platform is based on concepts similar to the open source movement which place tremendous importance on the value of freedom of both self and information.
By making rules overly prescriptive, it assumes bad intent from a community of contributors who contribute out of extremely good intent, which is a slap in the face. Further, compelling speech is a direct affront that many within the open source/free information community would find an explicit contradiction of values held dear by the community.
Finally, what this really signals is that the management of Stack Overflow are moving out of touch with the community. It has gone from a technical management that understand the values that drive the community forward through mutual respect and freedom and are instead driving towards something else entirely that I'm not even really sure how to describe, but it is at odds with core principles (freedom) of the type of person that makes an active Stack Exchange member.
For a rule to be effective and accepted in a community for which freedom is a core value, the rule really needs to be as minimally prescriptive as possible while still accomplishing its goal. Many believe this new CoC is far off the mark on that. The problem is not directly the goal, the problem is how they got there.
In addition to all of that, it's probably actually harmful to the group it's trying to protect, so it's also likely highly ineffective at accomplishing it's goal while also flying in the face of core tenets of the community.