Because of the reason his enemies are attacking him.
They are not attacking him because they believe he unfairly accused Shirley Sherrod of racism. They are attacking him because his opinions challenge leftist orthodoxy. The left has embraced demonization of those who disagree with them as a tactic for promoting their world view. In addition to this real reason for demonization, there is always a “good reason” offered to rationalize it, usually based on the claim that their opponent has violated some moral rule.
The specious nature of these “good reasons” is always obvious because of the double standard with which they are applied. More egregious violations of the same rules by those not perceived as enemies are ignored. For example, as noted above, Breitbart is being demonized for “race-baiting.” If the left held its own to a similar standard, few would be found in its ranks less guilty than Breitbart. In his case, it is not clear that he was deliberately making a false accusation of racism, or that Sherrod was even the main target of his attack. Whatever her intent when she made her remarks about discriminating against a white farmer because of the color of his skin, the approving reaction of the NAACP audience, which didn’t know at the time where she was going with her remarks, can certainly be plausibly described as racist. Regardless, the furious attacks on Breitbart continue, with all the usual faux virtuous indignation.
By way of contrast, consider the left’s response to a far more reprehensible justification of deliberate race baiting by one of its own. In an e-mail to his Journolist cohorts, Spencer Ackerman, who currently writes for Wired magazine and the Washington Independent, openly promoted false charges of racism as a political tactic. As noted by the Daily Caller,
In one instance, Spencer Ackerman of the Washington Independent urged his colleagues to deflect attention from Obama’s relationship with Wright by changing the subject. Pick one of Obama’s conservative critics, Ackerman wrote, “Fred Barnes, Karl Rove, who cares — and call them racists.”
Needless to say, this blatant advocacy of racism, providing only that it be exploited to promote a “good cause,” has not provoked the same contrived outrage on the left. The “good reason” for the attacks on Breitbart doesn’t apply to Ackerman, or anyone else the left considers one of its own.
All this is easily understandable in terms of human nature. We are wired to apply different standards to “us” than we apply to “them.” The left’s attempts to demonize the likes of Rush Limbaugh, Sean Hannity, Sarah Palin, Andrew Breitbart, and the rest of its pantheon of evil are perfectly natural. They are also irrational and self-destructive.
UPDATE: Who do you think David Letterman is picking on?
a. Spencer Ackerman
b. Andrew Breitbart