Oh, I don't think Earth's actions or inactions here are grounds for much debate. The colonists rebelled and said "You stay out!". Earth tried to talk to them, while no doubt preparing to do other things as well. And then the colony fell silent.
We don't know what Earth said, or what else she did or planned to do. We just know Earth decided the colony had failed for unknown reasons, in which case sending another would indeed be quite foolish. Surely the next sensible step would be to send out a scouting mission, something they had thought they could skip on the first try. And that scouting trip was then delayed when the warp 5 engine didn't quite materialize, and the Vulcans kept saying no, and so forth...
As for taking the planet from the 200 rebels, I'm not sure if that would have been technologically viable. Planetary assault would be quite new to Earthlings, and they'd have to do it without any sort of reinforcements. Even if the worst those hillbillies had was that endless cache of submachine guns, they could probably still make short work of any attempt at establishing a second colony: they'd know the terrain, and the second colonist wave would still be just as susceptible to acute lead poisoning as any colonists in Earth history. Starship technology wouldn't alter that any.
Timo Saloniemi