Just to infect them with malaria.
Homeopathy was used in the past to treat and prevent malaria but largely fell into disuse with the emerging dominance of the pharmaceutical industry. Today, people are taking a second look and finding that homeopathy is still useful in the fight against malaria. It is also safe, inexpensive, and free of parasite resistance.
No, we don’t have to kill them as they would kill others. Just infect them with malaria and watch them using their homeopathy to treat it.