1. Babies are not God's. They are the mother and father's. God, even if he existed, would have no rightful claim to them.
2. There's a difference between a baby and a first-trimester fetus. Big difference. Like, um, sentience. And, um, personhood.
3. Even if babies/fetuses did belong to God, that wouldn't make abortion wrong, according to Christian logic: If God existed, all the "non-believers" would technically belong to him, too, but that didn't stop Christians from massacring them left and right. And Tiller would belong to God, too, but that didn't stop Roeder from killing him...
4. Technically, giving something to God would involve killing it...so you're kind of stepping on your own argument there...
5. A serial killer is someone who murders a series of people. Tiller did no such thing. Roeder, on the other hand, killed an sentient, innocent man. Methinks you have their fates backwards.
6. So somehow, allowing women to exercise free will with their own bodies makes Tiller a serial-killing sociopath...quite the leap... And yet, "putting Tiller out of business", as you call it, isn't AT ALL indicative of sociopathy...or killing... Wow...
In short, you fail.