Liberals are Stupid, and Conservatives are Evil

The first: Because (left-)liberals won't face facts about human evil, but will assert that it exists only in people who are in power and who claim that it exists in people who aren't in power. Because liberals will believe that turning the other cheek and extending the olive branch will ultimately work, as long as you keep trying and don't resort to violence. Because liberals believe that all people will be good if they have enough of the basic material necessities for leading a decent life. Because liberals believe that it isn't cowardly but courageous to believe that if you just go forth with love and goodness in your heart, everything will be okay - poor or brown wrongdoers will be brought to tears in response (not the rich white ones - they're incorrigible), there will be a group hug, and we'll have world peace and prosperity.

The second: Because conservatives don't share those beliefs.

Actually, neither is really true. Conservatives, as such, aren't evil. They're realistic. Liberals aren't exactly stupid. Many liberals have loads of degrees and high IQs. But they do tend to the naive, quixotic, dogmatic and cowardly. These traits can appear to be stupidity to the observer. Ironically, in full flower, liberals are genuinely evil (e.g., when they steal from the rich or support the evil side in cases of armed conflict). Also, there is a certain simplicity, almost a dull streak in conservatism. If you're content with good ways of life, your mind doesn't race around like a monkey. So, there is something to "Liberals are evil, and conservatives are stupid," too.