They confuse objective claims with subjective ones.
When pro-life advocates say that elective abortion is morally wrong because it unjustly takes the life of a defenseless child, they are making a particular type of claim. Specifically, they are making a moral claim about the rightness or wrongness of abortion.
Those who are pro-choice often misconstrue the kind of claim the pro-lifer is making in order to respond to one they like better, which is a subjective claim.
Consider the following pro-choice responses to the moral claim of pro-lifers.
"That's just your view."
As a guest on the television show Politically Incorrect, former super-model Kathy Ireland gave a carefully reasoned scientific and philosophic defense of the pro-life position. The show's host, Bill Maher, ignored her evidence completely and shot back with (paraphrase) "Kathy, that's just your view."
What's wrong with this response? Maher was confusing a moral claim with a preference claim. There is a difference between disliking something and thinking it is morally wrong. When pro-life advocates say that abortion is morally wrong, they are not saying that they personally dislike abortion or would prefer that people not have one. They are making an objective, moral claim.
Imagine someone saying to you, "A space ship has landed on the roof." How would you respond to this claim? It would do no good to say, "That's just your view." To refute the claim you must show that it is false. The correct response is to say, "Your evidence is lousy. I looked on the roof and there isn't any space ship there."
At no point did Bill Maher challenge Kathy Ireland's facts and arguments. In effect what he said was "Go away, Kathy. You have your views and I have mine." Those who are pro-choice attempt to dismiss evidence rather than refute it. Maher was confusing a preference claim with a distinctly moral one. Subjective preference claims cannot be evaluated as true or false because they are matters of personal taste.
Kathy Ireland claimed that abortion is wrong because it takes the life of a defenseless child. She believed that she was right. Maher's glib answer did nothing to prove her wrong. In fact, one could stop Maher dead in his tracks by saying, "Bill, it's just your view that it's just my view."
"Don't force your morality on me."
A student at a Southern California college said this to Scott Klusendorf after he made a case for the pro-life position in her sociology class. She was in effect saying, "Morality is relative; it's up to me to decide what is right and wrong." This is called moral relativism, the belief that there are no objective standards of right and wrong, only personal preferences. Therefore, they insist that we should tolerate other views as being equal with our own.
Greg Koukl and Francis Beckwith point out that relativism is seriously flawed for at least three reasons. (For their full refutation of relativism see Relativism: Feet Firmly Planted in Mid-Air.)
First, relativism is self-refuting---it commits intellectual suicide. The student said it was wrong for Scott to force his views on others, but she could not live with her own rule. Although the dialogue was pleasant, she tried to force her views on him.
Scott summed up his conversation with the young lady, saying, "With all due respect, here's what I hear you saying. Unless I agree with you, you will not tolerate my view. Privately, you'll let me think whatever I want, but you don't want me to act as if my view is true. It seems you think tolerance is a virtue if and only if people agree with you."
Put succinctly, her argument for tolerance was in fact a patronizing form of intolerance. She spoke of moral neutrality, but tried to force her own views on Scott.
Second, it is impossible for a moral relativist to say that anything is wrong, including intolerance. If morals are relative, then who are you to say that I should be tolerant? Perhaps my individual morality says intolerance is just fine. Why, then, should I allow anyone to force tolerance on me as a virtue if my preference is intolerance?
A moral relativist cannot legitimately say that anything is wrong or truly evil. Greg Koukl once challenged a relativist with this question: "Do you think it is wrong to torture babies for fun?" She paused, then replied, "Well, I wouldn't want to do that to my baby." Greg responded, "That's not what I asked you. I didn't ask if you liked torturing babies for fun. I asked if it was wrong to torture babies for fun." The relativist was caught and she knew it.
Third, it is impossible to live as a moral relativist. As C. S. Lewis points out, a person who claims there is no objective morality will complain if you break a promise or cut in line. If you steal his stereo, he will protest loudly. Simply put, moral relativists inevitably make moral judgments. They espouse a view that they cannot live with.
Moral relativism is expressed one other way: "I'm personally opposed to abortion, but I still think it should be legal." When people say this to Scott Klusendorf, he asks why they personally oppose abortion. Invariably they reply, "I oppose it because it kills a human baby." At that point he merely repeats back their words. He says, "Let me see if I got this straight. You oppose abortion because it kills babies, but do you think it should be legal to kill babies?" Of course not.
Greg Koukl suggests this tactic: The next time somebody says that you shouldn't force your morality on them respond with only two words...why not? Any answer given will be an example of that person forcing his morality on you!
Proceed to the Mistake #2