To be clear I need to define a narcissist. A narcissist is a person with an excessive interest or admiration of themselves. Personality traits tend to be an over-inflated ego, a victim complex, an obsession with control of others, and desperate need to be flattered.
These personality traits are extremely toxic in any environment, but the toxicity is amplified in an environment without privacy. An environment where the narcissist can overhear any conversation and involve themselves in it.
An open office not only removes all privacy for everyone, they give a narcissist access to everyone.
This alone should be enough reason to abolish open offices, even if you ignore all the other things like microwaved fish and micromanagement.