Stacy McCain has a very insightful post. Excerpt:
This is how damaged people become monsters: They externalize their inner feelings of worthlessness as hatred of demonized scapegoats, whom they construct in their own minds as symbols of wrong, so that doing evil to the scapegoat is (in their twisted thinking) an act of righteousness. In the perverted mind of the obsessive sociopath, hatred of the scapegoat is thereby endowed with a heroic quality.
The peculiar “heroic hatred” directed at Andrew Breitbart by these monsters is not merely the product of politics, but rather an obverse reflection of their own damaged egos: Breitbart was famous and successful; they are obscure failures; his fame and success must therefore be re-imagined by them as unjust and symbolically evil.
Precisely so. I have seen this exact pattern play itself out, again and again.