Why should we think that pro-social capabilities are simply not expressible by weight-based ANN architectures?

Assuming that means capabilities which are both comprehensive and robust, the burden of proof lies is in the other direction. Consider the range of other seemingly-simpler things which are still problematic, despite people pouring money into the investment-machine.

Even the best possible set of "pro-social" stochastic guardrails will backfire when someone twists the LLM's dreaming story-document into a tale of how an underdog protects "their" people through virtuous sabotage and assassination of evil overlords.