There are some similarities, but here's what I would say:
1. The Holocaust = Classifying certain folks as "parasites" merely because you don't like their religion or ethnic background simply does not make it true.
2. Slavery = A practice that unjustifiably infantilized both children and grown human beings for profit.
In the case of abortion, there's an objective, biological (and, in language that might please Timber, "natural rights") basis for viewing women as being in control of their own wombs.
And: in language that most certainly would *not* please Timber -- The U.S. government does not recognize you as a fully-fledged person until you are born.
What else makes slavery and the Holocaust different? Those victims were people!
Not unborn fetuses with no personal background, history, emotions, opinions, or perhaps any mental functions whatsoever of their own depending on the exact stage of fetal development.
Recall that Timber and folks like him want to ban abortion from the moment sperm touches egg. Taking Plan B 4 hours after intercourse, and partial-birth abortion, are exactly the same thing to them: murder.