It does discredit the testimony if you can show that the one testifying is biased in some way. If you put a self-declared Nazi on the stand and ask them to describe Jewish people, it wont be flattering, and you can't say that it is an objective truth. Sovereign has a bias against organic life, it's trying to kill us, so why should I trust it to tell the truth about us? Exactly! That's my point. Sovereign can claim that the Reapers are god-like and that organic life is an accident as much as it wants, but if it doesn't provide evidence for it's claims then why would you believe it? Well okay, I wont get into the philosphical distinction between belief and knowledge as that's beside the point, and it was my mistake in swerving off the path like that. However, the point was that you believe Sovereign is telling the truth and I believe it is not. Without evidence to support either of our positions, you can't claim that your position is more valid than my position, and vice versa. At least, that was the way things used to be, ME2 has now provided some evidence that the Reapers have their origins in organic life, which suggests that Sovereign wasn't telling the whole truth in ME1. If you want to continue to believe Sovereign and claim that ME2 contradicts ME1, there's nothing I can do to stop you, but I hope that you can see now why I don't see any contradictions as I didn't believe Sovereign's claims in the first place.