If you wish to defuse an argument, simply pointing out that party X holds to alternative II, and asking whether they can understand why party X holds to alternative II, should be enough to at least start smothering the fuse.

Sometimes, the only answer you can come up with for this is "Because they're mistaken, evil, or both." (We can probably agree today that anyone making serious pro-slavery arguments prior to the American Civil War was mistaken, evil, or both.)