The Nazis didn't just see the Jews as inferior. They saw every other ethnicity as inferior to Germans. The Jews were at the very bottom of the list of the inferior races, and they weren't just considered inferior and fit to be slaves; they were considered dangerous vermin which was to be exterminated. Final Solution was the state policy. There was no such policy on Cardassia towards Bajorans.And the Occupation of Bajor is only a loose parallel to the Holocaust perhaps, but there are some similarities. The Nazis thought that the Jews were inferior. The Cardassians thought that the Bajorans were inferior. The Nazis used Jews and other they deemed undesirables in death camps. So did the Cardassians. Other aspects of the real-life Holocaust that the Nazis did were explained on screen as part of the Bajoran occupation.
The fact that it's not a perfect match doesn't mean there are some similarities.
The theory of inferior and superior races was hardly the invention of the Nazis - they just brought it to the extreme. Scientific racism existed centuries earlier, and was very influential in the 19th century. It was used to justify slavery, as black Africans were pronounced fit for slavery because of their "primitive psychology" and general inferiority to the white race. Antisemitism was also rampant. Racial theory talked about the so-called "Nordic race" as the one responsible for the development of the Western civilization. It wasn't uncommon to display black Africans as animals in cages - World Fair 1889, for instance, had a "Negro village" as a major attraction - and they were often presented as a "missing link" between apes and humans.
You know what really pisses me off? It's not the fact that everyone keeps comparing Cardassians to Nazis even when the parallel really doesn't work. It's because it's a huge, dishonest cop-out. I know why people, including the show's writers, compare Cardassians (or their military, etc.) to Nazis. Because Nazis are today synonymous with evil, and Hitler is synonymous with Satan. Comparing someone with Hitler/the Nazis today, is the same thing as comparing someone with Lucifer and the demons in the Middle Ages. It's just a way to say "they are really evil, the worst of the worst" in an effective and safe way, because pretty much everyone in today's world, apart from a tiny minority of sickos, acknowledges that nazism and fascism was evil. But mention some other historical example of genocide, colonialism, exploitation, slavery, and you can actually cause controversy. (As seen in my "USS Cortez? Really?" thread. "Hitler was evil". Duh. Everyone knows that. "OK, let's talk about Cortez instead, that's more interesting". A can of worms opens...) And that's what really pisses me off - when people act like nazism was some sort of aberration that came out of nowhere and had nothing to do with the human history that came before, rather than what it really was, an extension and culmination of a long history of racism, imperialism and exploitation. No, let's just pretend none of that ever existed. Much more comfortable that way.