There are a lot of people who need to FEEL that abortion is not a Holocaust, because then they would have to admit that they are on the wrong side of a modern-day one. What is particularly sad is that 93% of Jewish people are in favor of abortion, despite the Tanach being clear on "Thou shalt not murder!" The typical Jewish rabbi response is that the fetus is not human - well, there goes that "science-y" thing!

Here is an avid comparison, including of the words used in both cases, words like "sub-human," "parasites," "mass," "evacuation," and "medical research" with citations:

http://www.abortionfacts.com/literature/abortion-the-hidden-holocaust

I also found this - showing that the kill rate is about the same:

http://www.godvoter.org/abortion-holocaust.html