This clip is from the Associated Press stylebook. It is used by newspapers across the country to provide guidelines in how stories should be written. By and large, many guidelines are neutral and simple are matters of style (i.e. capitalization, punctuation, etc). However, in this one entry, standing unique in comparison to the whole guide, the AP picks sides in the abortion debate and insists that the pro-abortion side be the one supported in news coverage.
If Planned Parenthood wants to use pro-choice and anti-abortion, that's their perogative. However, the Associated Press, as journalists, pretend to be objective in their reporting. In this case, they choose propaganda terms to portray those against abortion in the worst light and those who support it in the best light. Framing, apparently, is not just for politicians anymore.
The particularly interesting part of this guideline is that it is objectively false. The words pro-life and anti-abortion are simply not interchangeable. The largest pro-life group in the United States is the Roman Catholic Church with roughly 60 million members. Evangelical Christians, for as much press as they get, are a pittance in comparison to this number. Further, evangelicals and other Christian churches very quickly get highly variable on the issue of abortion, or for that matter, any "difficult" theological concept.
The US Catholic Church terms pro-life as including not only abortion, but contraception, capital punishment, euthanasia, stem cell research, cloning, and reproductive technologies. To pigeonhole the Catholic Church's pro-life stance as simply being against abortion is to disregard factual reporting and adopting lockstep propagandist talking points from Planned Parenthood. Lobbyists are free to do this, objective journalists should not be.
The media, at large, is just as guilty as the Associated Press on this point. They will not use the term pro-life if it can be avoided and in so doing, they give up objective reporting and become lobbyists. Here is a clear case were bias can be proven the next time someone suggests there is no bias in the press.