Ad Hominem -- the favored attack of the right.

This one is so easy I don't need to actually say anything myself, except this: When you can't defend your position, attack those who think you are wrong.

"What a copout,'' Carlson said Monday. "On the one hand, he wants to play media critic and cultural critic, and on the other hand, if challenged, he retreats into 'I'm just a comedian' mode. I mean, that's pathetic.''

Attacking the Person
(argumentum ad hominem)
Definition:

      The person presenting an argument is attacked instead of the
      argument itself. This takes many forms. For example, the
      person's character, nationality or religion may be attacked.
      Alternatively, it may be pointed out that a person stands to
      gain from a favourable outcome. Or, finally, a person may be
      attacked by association, or by the company he keeps.

      There are three major forms of Attacking the Person:
      (1) ad hominem (abusive): instead of attacking an assertion,
      the argument attacks the person who made the assertion.
      (2) ad hominem (circumstantial): instead of attacking an
      assertion the author points to the relationship between the
      person making the assertion and the person's circumstances.
      (3) ad hominem (tu quoque): this form of attack on the
      person notes that a person does not practise what he
      preaches.