I'm just gonna slip in here and massively disagree. Even with the contraceptive methods that we have, there are bound to be failures and mistakes. The quality of a pill can be ineffective - the really good ones are far more expensive, and not everyone can afford that. Same with condoms; cheaper ones are less durable, and if you've got a latex allergy then you're going to be spending more on allergy friendly Snickers wrappers. But even then, condoms can break. Pills can not be effective. The simple act of a man and woman having sex does not grant a baby permission to the womb, the two saying "Let's have a baby" does.
There is no scientific grounds to denying other people abortions. Even without religion, it relies on ethics and personal morals, which are beliefs. "I believe this is wrong, so what you're doing that has no effect on me should be illegal."
First....yes. Individual methods of birth control can fail. This is why multiple forms should be used. Look up the statistics; what are the odds that a woman's 'pill' will fail (she had a cold this month) AND the condom breaks, AND the spermicide didn't get all the little swimmers, AND the diaphragm ripped?
Personally, I think that a baby that shows up in the face of all that obstruction absolutely has earned the right to see if it can live through the next nine months.
Second: if we were talking about gay marriage or smoking pot or polygamy or a whole host of other things, I would agree with you. Those do not (in general) affect me. However, abortion?
Would you watch a woman put her newborn in a nest of rattlesnakes and do nothing because it 'doesn't affect you?" It doesn't, y'know.
Some things we resist because those things do affect our freedoms. Some things we resist because they injure the innocent--and can there be a more innocent (as in; completely free of guilt or responsibility for) human than a newly conceived human? I can't think of one.
BTW, I don't necessarily want to see abortion made illegal. At least, that's what my position used to be. I still want it UNTHINKABLE, so that the only time it is even considered is when the pregnancy causes grave risk to Mom, and even then it should be considered a tragedy and something to mourn, not celebrate over. Except for that, it should have a social stigma akin to putting roast toddler on the menu.
The longer I live, though, the more I think that a 'law against it' might be the only way to get there. Maybe if there was a 'law against it,' with very real consequences for both male and female involved, people might be more willing to actually think before they go have their jollies, and be more responsible about the birth control issue.
By the way, in cases of rape, I have come to think that, if the woman simply cannot handle the idea of bearing the child of her attacker and decides to abort the pregnancy, the rapist should be charged with murder.