That's unfair and a cheap shot. Lindzen is a member of the National Academy of Sciences and holds an endowed chair at the Massachusetts Institute of Technology. They don't give those to crackpots. The guys on RealClimate pay him a lot of respect, even as they counter his arguments--in fact, they pay him respect by taking them seriously enough to be countered. (That's how it should be in science.) In this November 2001 Scientific American profile of Lindzen, James Hansen says of one particular point of Lindzen's,
Goddard's Hansen says that by raising this possibility Lindzen has done a lot of good for the climate discussioneven as he thinks Lindzen is wrong.
If Lindzen is mostly right about anthropogenic global warming, he's certainly not "discredited." Even if he is mostly wrong about it, he is still credible. Einstein was wrong about the Copenhagen interpretation of quantum mechanics (the probabilistic interpretation of the wavefunction), but that did not make him discredited.
I'm sure Lindzen knows a hundred times more about the climate than Laurie David ever will, and that makes him more credible than her regardless of who is on the "right side" of the issue. I'd love to see a debate between the two.