Freedom of choice the freedom that all other freedom is based on.
That's why.
I have two main problems with abortion.
1. How can it be murder if I kill a woman's fetus at X months old, but if she kills the same fetus at the same age it's choice? This isn't logical because the entire pro abortion movement is based on the belief that before Y a fetus isn't a human, and as we discussed earlier murder is the illegal killing of a human being, well if in the case of abortion you can declare that a fetus under X is NOT a human then later on you can't just change your mind and say "okay in this case it IS a human , so we're charging murder" laws are supposed to be consistent.
Of course both sides just agreeing that at X a fetus becomes a baby would end that debate right there, but no one in any position of power wants to end debates, that would leave the rest of us time to investigate THEIR activities.
2. I think it's completely unfair that men are put in the position of not having ANY choice about whether they would like their fetus to grow up to be a baby, but on the other hand if they do NOT want a baby they also have no choice but to support said child should the mother decide to allow it to become a baby.
Notice that neither of my arguments stems from morality.