“It is easy to understand how even a federal agent could be intimidated into not carrying a gun in San Francisco, when he was not on duty.”
I am not sure I understand this. Why would he be any more intimidated than an off duty SF cop would be? Also, does current policy of federal (and state & local) law enforcement agencies allow leaving firearms in unattended personally-owned vehicles? In this case, the agent was found not to have violated policy but is the same generally true of current policy?
The BLM agent is not an employee of San Francisco, as SF police are. San Francisco is perhaps the most anti-gun jurisdiction in California.
While unlikely that an off duty BLM officer would be arrested and jailed, the possibility of being detained was real.
I would have made the decision to have the firearm on me. The officer did not.