It's that I have a special kind of disdain for people who can't ever admit they were wrong.
Whether it is flat-out insistence on something in the face of clear contradictory evidence, or just gradually diluting and titrating what you say until your original assertion is ignored, neutralized and forgotten, it's annoying, childish and cowardly. Very unbecoming.
Gah, politics. People shouldn't be allowed to govern themselves in groups larger than 30.