If you think the fetus is a person, then that person is a minor who can't give consent anyway. In which case the parents give consent, so that argument doesn't hold any weight.
First, you have an
expanding cirlces argument issue in that if protecting life is so important, then that should expand to protecting animal life and then expand to protecting plant life; however, humans must take life even in order to simply survive.
What you probably mean to say is "human life" as being important to protect. But a liver or a kidney is also "human life" in that it's human DNA and it's alive.
So then you need to be more narrow and say "person's life" is important to protect, which falls back into the problem of when do we consider the transition from a bunch of cells to being a person. That's very dependent on how you define "person", and we're back to the same point this issue is focused around: differing definitions of a person.
And that's also where your analogy breaks down: Nazism, Stalin, etc. were definitely killing people, but this isn't true for abortion depending on your definition.