There are plenty of defenses against drones better than firearms. The primary means of disabling drones is hacking their communications. This is how Iran brought down the Predator, and how most of the drones that were used in a swarm to attack the Russian base in Syria more recently.

If you think about it, firearms aren't designed to disable devices, but things made of meat. There are better ways of disabling machines, and many of those means can also turn those devices from threats into assets.