If the Ba'ku were so...enlightened and nice, for lack of better words, why wouldn't they just share the planet with others for the purpose of helping others?
Or better still, abandon the planet so the particles could be collected and distributed across Sona and Federation space. That way people wouldn't have to travel to the ring planet, the rings would travel to them.
They were selfish.
Very much so.
Anij: "There's an unusual metaphasic radiation coming from the planet's rings. It continuously regenerates our genetic structure."
Why would it be necessary to ask them, they knew exactly what the rings did. When Picard explain what the Federation and the Sona planned, the Baku should have immediately
said: "The particles will help hundreds of billions of people, as they helped us? How soon can you beam us up?
But they didn't ... selfish assholes.
Picard's meeting with Anij occurred about one third of the way through the movie.
Who was following the instructions of the Federation Council.
Who were doing their jobs of looking after the best interests of the hundreds of billions of people in the 150 member Federation, and not just looking at 600 people living in one valley, on one Federation planet.
the bad guy in these situations
Really the Baku were the bad guys. Nice looking blonde hippie bad guys.
planning to kidnap the natives and never let them know what was going on.
While the children seen in the movie were "natives," the adult Baku weren't. They were migrants.
Given that it was a Federation planet, nothing should have been kept secret, the Baku should have been simply evicted.