Wait, you said you're talking about morality and then said "legally obligated". So you're not talking about just morality, you're also talking about the legality of it. So answer my question: why are you legally obligated to do this, but not to donate your organs to your children?
You do realize the morning after pill is fairly expensive, right? What of a family living paycheck-to-paycheck that are being responsible but the condom broke and they can't afford the 50-100 dollar sudden expense? Now that woman is probably going to be out of work for a time to have the child, on top of the medical expenses a pregnancy carries with it. When they were perfectly responsible, just poor.
The pill is not the reason for "augmented promiscuity", not that promiscuity is even a bad thing to begin with (you have no right to judge someone else's sex life as long as they're not harming you). As someone who is actively on the pill and have been for years, you're teetering on the edge of being very offensive. Please watch what you say and the judgments you pass on people whose lives you don't know a single thing about.
An abortion is more expensive, invasive, painful, and difficult than birth control. Scare tactics about "women using abortion as birth control" are red herrings. Do you have any evidence that shows a significant amount of women using it as birth control now? Or did you just hear that once and it stuck in your head and now you think it's a legit argument? Because without any evidence, I don't see how you can even express this as a problem when every logical argument points to it not making sense.
Yes, it's also not murder for you not to donate your organs to someone who needs an organ and then they die, but it is murder if you kill them. Funny how that works. My body is my own. I am under no obligation of any kind to let a person leech off of my organs, my blood, my nourishment, my womb, for any period of time. If the fetus can't survive outside of my womb, that does not mean it's my responsibility to donate my womb to the fetus; that means that it's unfortunate that it can't survive but I have the right to decide what is using my body, human or not.