What makes you think there is a minimum competency test required for a government job?
In his case, hanging up on him simply provoked him to call again.
A broader contagion arises. ANY criminal who threatens illegal activity unless their demands are met must first be judged on the merits of their action and thoughts.
The last thing anybody should do is claim that the murderer's actions are caused by anybody but the murderer.
A counterargument might go,...the officer hung up because the rude murderer caused him to hang up. ....The officer's behavior might have actually saved another 10 people from being murdered.
Both are responsible for their respective behaviors. IMHO, I tend to give the benefit of the doubt to the cop.