I think it is because we have accidentally created a culture where it is embarrassing to admit ignorance or stupidity. A Lib faced with a Conservative point that is stronger than whatever he/she can come up with, either begins lying, BSing, or walks out, and a conservative will do the same. This only hurts us as individuals and as a country. If you can cough up the guts to say "I said/did something incorrect/stupid", or "I don't know", you are a superior being at this point.