The primary reason abortion is wrong is that God said that we are not to murder. But not all people believe what God says so let's look at it from a different angle.
We are allowed to take life under the prescribed requirements of law such as self-defense, war, execution, etc. Each of these areas deals with Law. Self- defense is justified because an antagonist is breaking the law (burglary, robbery, assault, etc.,), and we can use force to protect ourselves and our property. War is the legal declaration of hostilities towards another nation. Execution is the legal taking of life against someone who has committed a crime or crimes worthy of execution. In each case, the antagonists are dealt with for the wrongs they have committed.
However, the baby in the womb has done no wrong, yet it is executed. It is executed but has broken no law! What crime has been committed? What law have they broken in their existence? None. Yet they are killed.
I am reminded of Nazi Germany. The Jews were guilty of being Jews and were, according to the Nazis, worthy of death. Likewise, the babies in the womb are guilty of being babies in the womb and are, according to the parents, worthy of death. What laws did they break? What made them unworthy of life? The answer is simple: it depends on the opinion of those in power, of those wielding the knife and redefining what is life, and of those deciding who is worthy of life and who should die.
It is only in abortion that someone is executed but has not violated the law. This is fundamentally wrong, and this is why abortion is wrong.
Since when do we kill someone who's broken no law?
Since when do we kill someone whose only "crime" was being brought into existence via the copulation of his or her parents?
Some wars are not justified, and this argument overlooks that fact. Whether or not some wars are justified has no bearing on the argument. The context deals with that which is, hopefully, morally proper. Therefore, it is appropriate to take life in self-defense, war, and executions. And yes, we acknowledge that there are unjust wars and improper executions, but what does that have to do with destroying life in the womb? If it is improper to have war or to execute someone, why is it okay to kill the babies in the womb?