Even if he is right, he offered a political judgement. Since your morals come from your politics (and not the other way around), I can see how you would think his political judgement would be important.
But, you have offered no reason why I should care about Trump's comment.
As to the point in the body of your post: There are many historical examples of the public supporting homicides of entire groups of people merely for what those people were. In every case, "the public" was wrong. You should care about that.
Saying that an abortion is a killing is not a moral statement, so it is not extremist. I called it a homicide, which is a killing of one person by another, regardless of intention or legality. It is a scientific fact that an abortion ends a human life, and the fact that it is caused by another human makes it a homicide. There is no moral judgement there at all. In fact, we allow legally ending human lives, intentionally, in at least three cases (capital crime convicts, self-defense, and innocent babies...I just argue that one of those is not like the others). We also do not punish people for accidental homicides in many cases. But, it is revealing that in only one case, people try to call a homicide not a homicide. Obviously you have some discomfort with abortion if you can't look at it, and call it what it is. If you have to look away, and use euphemisms, perhaps you should ask yourself why you do that?
The "lack of concern" argument is false. You obviously don't know pro-lifers. But, perhaps your point is that pro-lifers need to advertise their equal concern for the mother more broadly and successfully, and with that I agree.
In the end, though, your point is political: "a conundrum for the GOP." But, I am not concerned with that at all, so Trump's point doesn't concern me. I'm not willing to define a class of humans as killable just to get a party I like into political power. That makes me very unlike you. Indeed, I am willing to sacrifice many of my non-moral political values to achieve the moral goal of saving the lives of innocents.