The things I'd tell them in response to your hypothetical:
* If somebody is attacking somebody with a deadly weapon, you don't use a stun-gun, and neither to do the police. You use a 9mm.
* In the unarmed scenario, you need two trained police officers. Two people, well-trained and with good teamwork, can usually restrain even a huge, out-of-control person.
If they can't, I advocate adding more peacekeepers (police officers or other trained citizens), not more weapons.
Additionally, the scenario you describe is fairly rare. I prefer adding what might seem like logistical inconveniences to very rare scenarios if it means adding clarity and peace to much more common ones.
(side note: a very senior practitioner in my lineage was kicked out of the association in large part because, as a police officer, he was found to have acted brutally and unethically - his name is not even mentioned at my dojo. That might give you a sense of the commitment to good purpose that at least some martial arts schools have regarding training agents of the state.)