Why do so many people think that pro-lifers either do or should find ALL human life valuable no matter what?

I am pro-life in that I acknowledge that it is wrong to deny an unborn child the right to life, but as far as I'm concerned that doesn't mean that I have to pretend that there aren't some people who deserve to die gruesome deaths as punishment for what they have done. In my eyes "pro-life" doesn't mean that I'm some pot-smoking, tree-hugging hippie who thinks that holding hands and ; it means that I recognize the irrefutable fact that innocent people don't deserve to die at any stage of life from the womb to the grave, and especially in the name of convenience for one or both of the would-be parents.