Well, someone could be discussing in good faith, articulate a principle that they believe represents their morality, reason out a consequence of that principle and then observably act in a contradictory manner.

(now that I have written that, I guess part of what I am getting at is that the more often that actually happens, the more you have to discount the articulation of moral principles rather than discounting the people or the good faith. Personally, I'm pretty optimistic about people and pretty cynical about the things they say...)