First is the attitude that the "poor" or "underprivileged" (which to a liberal usually means anyone whose skin is darker than his own) cannot make it without "our" help. Is it ironic that this, one of the most bigoted, elitist, patronizing attitudes in politics comes from the very people who use these terms to describe their conservative opponents? Considering human nature, it is indeed ironic but not surprising. The hypocrisy is amusing but the fact that most liberals are blind to this hypocrisy merely shows that the roots of elitism run deep.
Next is the notion that having good intentions is more important than achieving results. Most liberal efforts fail to achieve their objectives, and many actually produce the reverse of the intended effect. But the liberals go forward, undaunted, continuing to exacerbate the very problems they wanted to solve, because they know deep in their hearts that they have good intentions. What they don't realize is that good intentions can never justify the damage done by ill informed action.
Then we have the way liberals change or ignore the facts to suit their theories. But this is not strictly a "liberal" problem - conservatives do the same. And both liberals and conservatives use the worsening problems their own programs have helped to create, as an excuse for more of the same programs that caused them in the first place!
Finally we have the arrogance of the liberal creed. Because they have the best of intentions (just ask them), anybody who opposes them must be either ill informed or a bad person.
The most snarky conservatives (Coulter, Limbaugh, etc.) often ridicule the naivety of liberals, but they rarely impugn their motives. They see liberals as well meaning fools, often intelligent yet even more often naive. Imagine the following exchange:
You don't support the Kyoto agreement?
You must want the Earth to become a smoking wasteland!
You don't support government run schools?
You must be against education, or think it's only for the rich!
You don't support government run welfare?
You must want people to live in poverty!
Most people, when using arguments based on such transparently false dichotomies, do so knowingly and with a smirk. But the fervor with which liberals engage in this kind of debate belies the fact that their arrogance blinds them to the fallacy of their arguments.