Space Nuttery is thinking it's somehow important or relevant for humanity going forward.

A power source for a floating camera to go take pictures of dead rocks and frozen chemicals is a niche interest. No one has a RTG powered city.

"You can’t just hear the word space and declare it “nuttery”,"

You can't just hear "Space Nuttery" and talk about space. Space is a mostly empty sucking vacuum hostile to all life and a radiation-blasted hell.

Space Nuttery is living in a fantasy world where we'll just somehow go space mining and colonizing Mars with water from Saturn's rings like it's just a question of a longer trip to Home Depot.

It's an intellectual dead end.