Conservatives have a really hard time understanding why Democrats and their less honest counterparts in the Republican Party can lie so easily.  It doesn't really have anything to do with what they're telling you at the moment.  It's that they are trying to get you to believe ALL lies.  The government shutdown is a perfect example: several democrats will swear that this isn't about illegal immigrants.  Why, when it so obviously is?  It's part of a larger strategy.