Tali'Zora and Kal'Reegar. Quarians all the way.
Moral Justification for the Quarians: They did not intentionally make the Geth sapient. What I gathered from the Codex and Tali's conversations is that they created quarianoid (Is that the right word?) robots to do menial labor tasks. They wanted them to be able to do more varied tasks, so they increased their intelligence in small bursts, until they (presumably unintentionally)became sapient. They panicked and tried to destroy all the Geth, but being sapient, they would not stand for it, and organized a rebellion. They were wiped out because they underestimated their opponent. They believed that most of the Geth were still just machines, and did not prepare for full scale war. When it was shown the Geth were mostly sapient, and capable of organized resistance, thye got their asses kicked because they were prepared basically for fighting something akin to bipedal Roomba vacuums, not thinking organisms.
