I'm generally against the cruel treatment of animals. Although I'm 100% against the PETA.
Abortian can be seen as a form of passive eugenics. The unwanted are destroyed before youth. (I'm actually all for dangerous toys for all ages. Survival of the fittest should start at childbirth.) The fact that, although smart people have a better chance of survival, stupid people breed faster than smart people. Okay, if one child has a survival rate of 90% and is smart and another has a survival rate of 20%, it skews the results when there are only ten 90% kids but ten thousand 20% kids. (This should scare people.)
And although you say that a child should be given the right of any other living sentient, a fetus cannot live outside the womb (well, not for long). If teh child is unwanted, it is a parasite. Feeding off the mothers resources (including money) and taking what it needs for its life, regardless of the mother. If the child is wanted, she is freely giving these resources. Something to think of.
And back to the issue of women. How would you like it if something was growing in you that would cause your belly to grow large, your ankles to swell making it hard to walk, work, etc, cause you to throw up every morning, feel terrible, etc. Then, after nine months, go through terrible pains as it rips out of your body. If you wanted to be a mother, no problem, you know what your getting yourself into and your kinda looking forward to it. Now imagine your a sixteen year old girl (*****, incest, boyfriend whatever). Do you really want to go through that? Do you have the resources, financially, mentally, and physically? Are you going to get support from friends or family? Just another thing to think about.
