I've never seen you this enthusiastic about a thread before.
The best way to have handled this was to get to know the Vissians first, form a friendship, and then when the time is right, using great tact and care, open a discussion with them about human beliefs and practices, God-given rights, so on and so forth, ask them about the cogenitors, and tell them what you think(as humans) of the cogenitors.
They were, and would have been very receptive, and probably still would be receptive after the events of the episode, but if the situation were handled differently, no one would have died. Trip forced a situation where Archer was forced to choose between allowing the cogenitor to stay aboard or sending her back. He really only ever had one option besides making enemies of the Vissians(which would ensure that all the other cogenitors would continue to live as they do).
You find out its an error and you're returned to Earth. You may not be suicidal but it'd be a gut punch. Now double that because you're not a slave like the Cogenitor and then again because you're never going to be allowed to read or use the internet again again.
If Archer had not returned her, she would have lived a life (on Earth?) as a free person? What about all the other cogenitors? Who's going to help them? Not humans, that's for sure. The Vissians would be outraged, and weary of any Earth ships in the future. Not to mention if Archer had not returned her, the Vissians would be sending petitions to Starfleet Command, Earth's governments, the Vulcans, et al, and someone with more authority than Archer would send her back anyway.