YMMV / The Twilight Zone (1959) S5E18: "Black Leather Jackets"

• Complete Monster: The leader of the alien race wishes to overtake and colonize Earth. Claiming humans are evil and barbaric, he sends out thousands of aliens disguised as humans to poison the city's water supply with bacteria, leading to the extinction of human life. When the alien Scotty falls in love with a human and attempts to show that humans are not all bad, the leader simply labels him a traitor and sends him off to his fate, while starting to invade Earth.

---