The argument ad nazism is a form of guilt by association and or appeal to consequences. It is most often used by the anti-atheist and anti-evolution people as an attack on atheism or evolution (and is a big part of Expelled so I've read) the arguments are basically "Hitler, Stalin and Mow where atheist" or "Evolution was responsible of naziam and the holocaust" the implications being that atheism leads to immorality and evolution leads to social darwinism, basically a bunch of fallacious bullshit.
Atheism does not lead to immorality (see Secular Morality) and evolution does not lead to social darwinism. Evolution is about natural selection, those that have traits that give a creature a better chance at survival and reproduction. Killing innocent people is not a trait that increases you chance at survival and reproduction, it diminishes it and artificially selecting for trivial traits like blond hair blue eye do not increase any one chances of survival and reproduction.

Why do I bring this up? Whats with the title? What is Skeptico?
Skeptico has a grate post

This won’t be news to any rational people, but it may be news to creationists. And I know the subject has already been dealt with by numerous others, but this creationist post (also here – highlight the text after “spoiler” at the bottom), describing PZ’s recent expulsion from the creationist movie “Expelled”, describes some “specific content” of the film that I think needs a reply. It’s this:

Many scenes are centered around the Berlin Wall, and Ben Stein being Jewish actually visits many death camps and death showers. In fact, Nazi Germany is the thread that ties everything in the movie together. Evolution leads to atheism leads to eugenics leads to Holocaust and Nazi Germany.

Really creationists? That’s what you’re going with? Really? Well OK, if that’s the approach the religious creationists want to take, I’m happy to debate that point. There are (at least) three reasons why this isn’t a valid argument against evolution. Each one by itself is enough to sink this ridiculous creationist canard. They are:

1. So what?
2. Hitler wasn’t inspired by evolution
3. Hitler was religiously inspired

He then goes on to show how Hitler wasn't inspired by evolution and did have some religious (Christan) inspiration