You're not answering the question. What concession? What do a bunch of old people in the clouds of Venus have to bargain with? What resources do they control?

They aren't bargaining with the colony, they're bargaining with the nation that sent its citizens there (or any nation that views the survival of the colony as important enough to make other concessions).

It's like a criminal that points a gun at your kid and threatens to shoot unless you do X.