It usually comes down to that and people like you end up showing your true motivation. In the end, you simply hate Christians. Like most atheists, it's not enough to be agnostic, it requires you to attack. So you attack our beliefs out of your own hatred.
Is stealing wrong? Is murder wrong? Is rape wrong? Is cheating on your wife or husband wrong?
I'm going to assume that you will agree that those things are wrong. They're not wrong because they're in the Bible. They're not wrong because our Heavenly Father told us they're wrong. Those things are in the Bible because they are wrong. Our (as in yours and mine) Heavenly Father requires that we not do those things because they are wrong.
You assume that we don't believe in Christianity but are forced to it and have no will or choice of our own. That's not any more the case for us than it is the case that you're forced into your hatred for us. We choose God just as you choose to hate us for choosing God. Choices, all around.
So, it isn't that we're Christians, or of any other particular faith, that tells us that abortion is wrong; it's our inherent humanity and morality. Presumably, even you have some of that inherent humanity and morality because, I assume, you don't steal, rape,. or cheat on your wife. You're just so caught up in your hate for God and His believers that you are confused.
What you really should be doing is looking inside of yourself to understand from where that hate comes and realize that taking it out on innocent babies does not undo the hurt in you.