1) You really didn't learn everything you needed to know in kindergarten: Liberals love to think of themselves as sophisticated, nuanced intellectuals, but the truth is they have a kindergartner’s view of the world. If it has been defined as "nice" to people they like, they're for it. If it has been defined as "mean" to people they like, they’re against it -- and that is about as deep as it gets. Unfortunately, that lack of adult perspective isn't so cute in political leaders who are making life and death decisions that may still have ramifications fifty years from now.
2) "Liberals hate religion because politics is a religion substitute for liberals and they can't stand the competition." -- Ann Coulter: Somewhat ironically, given the hostile relationship that has developed between the Left and Christianity, liberal beliefs have more in common with religious doctrine than a political agenda. There is no significant debate on the Left about the aims of their agenda -- and the only "sins" believers can commit against their religion are no longer being politically useful, deviating from doctrine, or worst of all, cooperating with conservatives in some fashion. No matter how much evidence piles up that big government doesn't work, that welfare destroys families, and that socialism doesn't bring prosperity, it makes no impact on liberals because their dogma is based on faith, not logic.
3) "It is not human nature we should accuse but the despicable conventions that pervert it." -- Denis Diderot: There is no dream more eternal in the liberal heart than completely remaking human nature. If we could all just care about the person across the world as much as we do our families, we could live in a utopia! Unfortunately, in practice, human nature tends to be quite a bit more difficult to subvert than in the liberal imagination. That's why, despite more than 5,000 years of human civilization, very little progress has been made in this area – but, oh, the Left is still trying. One day, if they just spend enough money on the right government programs, all the wars will end and everyone will be living in identical million dollar mansions while we spend our days humming tunes from the latest Woodstock Tribute Album.