It a matter of opinion when human life begins, fact is though that an unborn baby is in a womans body and everyone should have control over their own body!! I can't see the difference between the decission to have an abortion and the decission not to donate your blood or second kidney or lung to some distant relative, who you've never met, in order to save their lives.
Both involve a decision relating to one's own body which will decide whether another person lives or dies but no one would dare call someone who doesn't donate a murderer.
I know a lot of people will prabably think that there is no comparison between these two but its no more of a leap than to call abortion murder