Pyongyang has every right to assert control over its sovereign territory. Not only is the South dropping propaganda leaflets into enemy territory, but it's doing so by flying drones all the way into North Korea's capital city. This is clearly a national security threat that must be dealt with by the North Korean defense forces.
Pyongyang is throwing a fit over leaflets that contain anti-Kim Jong Un messages. Besides the fact that these are just words, the only evidence of drones has been a single black-and-white photo of a winged object in the sky. South Korea has dealt with incoming North Korean drones for years, so for Kim to threaten bombs over this is uncalled for.
There's an 18% chance that World Population Review will declare that North and South Korea are at war before 2050, according to the Metaculus prediction community.