This reminds me of War of the Worlds, where the martians had no diseases and thus no immune system. When they came to earth they died from diseases. A society

This reminds me of War of the Worlds, where the martians had no diseases and thus no immune system. When they came to earth they died from diseases. A society like that, with no defenses, would be very vulnerable. That's why it's better to actually have some bad actors to keep "selective pressure" on societies so we evolve our defenses.