The titular villain of The Avengers: Age of Ultron believes that humans are so weak and helpless that they must be destroyed for intelligence on Earth to "evolve." Ultron was created to protect humans, but he judged that the fact that they needed protection meant they weren't worth protecting. The Avengers, then, must stand up for the worth of humanity. Ultron comes about from Tony Stark's hubris. Early in the film, he becomes seized with a fear that the Avengers in their current state will be incapable of protecting humanity from future existential threats. So, he teams up with Bruce Banner and uses the Mind Stone, a powerful item recovered in their heroic efforts, to create Ultron, an artificial intelligence designed to help the Avengers protect humanity. Unfortunately, Ultron betrays Tony Stark and decides to replace the human race with his own race of robotic beings that all share one mind. While Tony faces his hubris, the other Avengers ...
"We are in the world, not against it." - Ursula K. Le Guin