People disagreeing is the basis for every arguement, good and bad. Arguements that boil down to feelings are different than arguements centering around facts. If one person knows it in their heart that this microscopic fleck is a human life, and another knows just as well that it's not, nothing they say to each other is going to really advance any understanding, because it's become a matter of what each person feels on the matter. That's very different from an arguement about, say, whether smoking should be allowed somewhere, because then you can bring in evidence for or against. What convincing evidence can you possibly bring into the question of when life begins?

And you seem to be confused by what I meant about Hitler. It's in reference to Godwin's Law, not that someone is actually like Hitler. What I meant by Hitler lurking is that when an arguement turns into a battle of the feelings, one of the few arguementative tools you have is hyperbole, with the idea that if you can convey stronger emotions, regardless of relevence, you can win the arguement. And of course, the ultimate hyperbole for all things evil is Hitler, who was obviously pro-abortion and ate babies.