See, that is worth debating about, when. There is a point early on where it isn't, in fact two thirds of abortions are performed in the first trimester, the first thirteen weeks. It's at the tail end of this period that brain activity begins, it's in the second trimester that more interactive motions take place, such as kicking, sucking, swallowing, and apparently also dreaming. By the tail end of the first 13 weeks, I personally would be against an abortion, but the mother-to-be has had plenty of time to find out she's pregnant and be responsible for stopping the process before it's too late to avoid turning off a functioning human body (however small). IMO second trimester is too late, unless in very unfortunate and difficult cases of severe birth defect. The first trimester gives you three months to get your shit together.
Again, I personally would call it before even the end of the first trimester. Brain activity has already begun by the end of it, if I were to give a cut off date, I'd argue around week 10. Still plenty of time to figure out what you're going to do, and how, before an abortion starts crossing into ethical boundaries, before it starts to actually become a human baby, both in physical form, and brain development. There's a clock ticking on that, this is why wait times on meeting with a doctor are such a big deal, they can turn an otherwise (still unfortunate) easy and victimless procedure (unless you count hypothetical life to be a victim, which I understand and agree with to a point; the loss of potential prior to existence is worth talking about), into a much more ethical grey area, and there isn't a single person who comes out of that happily. No one wants to get an abortion, no one who gets one thinks ahead of time, "Man I just can't wait to accidentally get pregnant so I can have an abortion." it's just a thing that has to be done if you can't properly raise a child. I was actually conceived because my mother got one, because she had to, even though she didn't want to, and had a sort of relapse, met my dad and had a kid. I wish she didn't. If people can't afford children, it's cruel to force a consciousness into experiencing the world if you can't care for them. Plenty of people are evidence of this, though I am not saying everyone is the same, of course.

I agree that late abortions are a form of murder. I do think there's something to be said about the death of potential, but I also think there's something to be said about shutting off a brain before it's had a chance to experience and be alive. It's murder in the sense that an active brain is being shut off, but it's not the same as killing a born, experiencing, aware, interactive child, or a full grown adult, people who have had a chance to exist. Of course the closer you get to birth, the closer these two forms of existence become (in the womb :: in the world).

In case this personal fact matters in the scope of this argument, I'm asexual. I've been asexual my entire life, so I have no reason to be defensive about sexual activity. I do believe that if birth control fails, I'd notice right away and deal with it before the tenth week. No child deserves to be subjected to my impoverished, dysfunctional life. That is a harsher cruelty than aborting a clump of ambiguous human cells.

TLDR; In conclusion, my answer is around week 10, before brain activity begins. This is not considering birth defects and so on.