The reason would be to avoid that person spreading the fatal disease, thereby avoiding M deaths at the cost of 1 death. Killing the patient avoids a greater har

The reason would be to avoid that person spreading the fatal disease, thereby avoiding M deaths at the cost of 1 death. Killing the patient avoids a greater harm than letting them walk out of the healthcare facility. This isn't a personal interpretation, it's raw math, and it occurs in every society where the "public good" outweighs individual rights.