It started out with a simple enough statement: "Abortion is not like ice cream." But that was, perhaps, where the simplicity ended. It was certainly long gone by the time the word "murder" entered the picture.
In a lot of ways the whole point behind the quip, "If you don't like abortions, don't have one," is that it's an assertion that while whether or not an abortion is a homicide is often debatable, in jurisdictions where the practice is allowed, when performed properly, it is not a murder. Murder is best taken as a legal term, not an ethical or religious one. And it's an important distinction to make. (This is, after all, one of the things that worries many secularists about the highly religious - the idea that given the chance, the faithful would force their beliefs on others by codifying them into law.) Because, when it really comes down to it, regardless of how distasteful an action may be, if it's not illegal - it's a choice. Pithy catchphrases are admittedly glib, but the reason that this particular one is so often used is that once you assume that the choice of which ethical or religious path one will chose from a number of options is a personal one, it's effect on the grand scheme of things is no more consequential. The same is not true of legality. I may choose to break the law, or I may not, but the very nature of the law means that this not merely a personal preference.
The Judeo-Christian/Moslem emphasis on the existence of an absolute truth and absolute obedience to the will of the divine is often at odds with a more secular understanding of the world - and even those of religious traditions that are less absolutist in nature. In the Bible, even in the new Testament, there is often a legalistic understanding of morality and ethics:
For whoever observes all the Law but makes a false step in one point, he has become an offender against them all.And this understanding has carried forward to the present. And this often creates friction for the same reasons that secular laws do - legalism doesn't care what one believes or thinks is legitimate or not. The Law is the Law. An action is either illegal or it isn't. It may be the work of weeks by an expert to determine which side of that line an action falls on, but it falls on one side or the other. It can be (imperfectly) analogized as a Boolean function - for any given action under a given unique set of circumstances, the question of whether or not it's legal must always be either "Yes," or "No." And this is precisely why legalism tends to lend itself to black and white thinking.
The Letter of James 2:10
But once an action is determined to be legal, either because it's specifically allowed, or the law doesn't concern itself with it, under the law it's not much different from any other legal action, regardless of any other consequences that they may have. If I observe that my neighbor is in grave peril, the fact that United States law doesn't observe a generalized Duty to Rescue means that my choice of whether or not I decide to come to their aid is no more legally important than whether I have lemonade or white wine with dinner, even though from a moral and/or ethical standpoint determining whether or not another person lives or dies may be considered infinitely weightier than a beverage choice. It's possible to appeal to Natural Law, but until that earns a place in the criminal code, it's law in name only.
Given this, it's often difficult to talk about the choice of abortion in any other terms. If you don't believe that something is a "must not do," how else do you convey that, other than couching it in the language of choice? (There's a reason, other than simple euphemism, why it's called "pro-choice.") If you don't like abortions, then... what? What do you say to someone in that situation? What can be thought of as being both true to the idea that people should be allowed to decide for themselves and respectful of the idea that they shouldn't? (And vice-versa.) "If you are opposed to abortion, then they are not the right choice for you," sounds more formal, but is it really any different? As near as I can see, the sentiment is the same.
I don't know that there's ever a good way to bridge the chasm between absolutes and choices. Or the distrust that tends to fester in that abyss.