The dissonance between player choices and the story is at its lowest on the DLC. Not even the writers could come up with an excuse for your character to choose the "bad" side when someone directly asks you why you would even consider it.
Hmmmm...
I assume the bad ending is giving it to the daughter so she can make moola? I think she offers some nod to morality by saying she can fix the formula and save the barbarians or whatever they're called, while the mother just wants to ignore the problem. I could be misremembering though. I couldn't get the "make them work together" ending as I couldn't pass the skill check.