It's called Pro-choice because it gives women a choice. The debate on abortion isn't about forcing women to not have abortions and forcing women to have abortions. It's about allowing people to have a choice.
I'm not saying this in a rude tone, so please try not to take it that way.
I realized later on I didn't word it the way I wanted to. I still can't think of a way to word it. This sounds ignorant, but I guess I meant the opposite of pro-choice should have more to do with choice and not life. An extremely stupid example: pro-nochoice.
I'm not taking any side in this post. It's more of a language thing. Like, why is the opposite of pro-life pro-choice?
It's all spin. No one wants to call themselves the "death" side or "pro-abortion" side.
Likewise, the pro-life side doesn't want to call themselves the "anti-choice" side. I think the most logical names are pro-choice and anti-abortion, because the pro-lifers aren't always against war and death penalty, and pro-choicers don't generally advocate abortions all the time or casually.
The opposite of pro-life is pro-choice because pro-choice allows options, a choice. Pro-life doesn't.