In The Martian Chronicles, you can choose your own isolation adventure: you can be totally alone, like Gripp at the beginning of "The Silent Towns;" or you can just feel alone, like Spender at the beginning of "—And The Moon Be Still As Bright." Sure, Bradbury shows that crowds and large groups of people can be scary (see the crowd in "The Martian"—or in his short story "The Crowd"). That doesn't mean he's pro-isolation. Being alone is not presented in a positive light in The Martian Chronicles, but it can be even worse to be surrounded by people who don't see things the way you do. The lesson here? Befriend a nice group of like-minded people. Okay, Ray, we'll get right on that.
In The Martian Chronicles, isolation is the worst fate people can imagine. Characters like Spender and the Martian (from "The Martian") would rather die than be alone.
Bradbury suggests that isolation is key to figuring out one's true identity.