There's only one basic question about the Holocaust: Did the Nazis murder millions of Jews? The "yes" answer is supported by all the evidence. It's not nearly as complicated as the GW question. For the Holocaust question to be as complex as GW, you'd have to ask questions like:
- Did it actually happen in the first place?
- Even if it did happen, how do we know the Nazis did it?
- If it did happen, was it bad?
- Is genocide of Jews a natural occurrence that happens periodically because of forces over which we have no control?
The answers to those questions are easy; the proof is overwhelming, the case for alternative theories is scanty at best, and there has been no significant change in our conclusions over the past half-century.
Unfortunately, none of that is true about GW. Not every scientist who is skeptical about GW or its causes is a corrupt Exxon lackey, and not everyone with irrefutable proof of GW come to the table without biases or with his science straight (
see the unfortunate "hockey stick" study). I think it's perfectly fair for a layman to say about GW, "I don't know, and I don't understand enough about the scientific discussion to have an intelligent opinion," while being satisfied with history's final judgment about the Holocaust.