Regardless of sexual orientation, husband or wife is acceptable in all references to individuals in any legally recognized marriage. Spouse or partner may be used if requested.
AP is a news organization, and its style guide, which encourages text to be concise and headlines short, is designed for newspapers. This update could easily be seen as a reaction to the recent legalization of same-sex marriages in many US states. Unfortunately, the situation isn’t that simple.
Specifying usage of terms like these–terms meant to refer to specific gender roles that have been repurposed to apply to same-sex relationships–is a difficult line to walk. If AP were to suggest using “spouse” or “partner” for same-sex husbands or wives, as they did in a recent, arguably misguided entry to their Q&A, it would make the organization seem hostile towards the LGBTQ community.
The concept of marriage itself contains a legacy of ownership, of “ties that bind”. When it comes to projecting an image of impartiality, saying that husband and wife are acceptable to all is no better than restricting them to a marriage between a man and a woman only.
Husband comes from the words “hus” and “bondi”–the former meant “house” and the latter had meanings that included “dweller” and “freeholder”. This seems to imply landowning, or perhaps wealth.
The roots of wife are less clear. Proposed source words included the meanings “girl”, “bitch” (from the Dutch wiif), and possibly the meaning “to twist, turn, wrap” from the Proto-Indo-European suffix weip. With a shadowy past like this, perhaps it’s time to retire “husband” and “wife” entirely and look for new terms.
Using words outside of their original meanings can be perilous. While I personally feel that any two consenting adults can get married, I can see how difficult AP’s situation is: There’s no possible way that they can provide guidance to journalists on how to use the terms husband and wife without appearing to take “sides” in the current debate over same-sex marriage. Arguments about the advisability of involving the government in the private affairs of consenting adults to one side, the linguistic roots of these terms may well play a role.
Ultimately, publications that want to write impartial articles will do so, and “journalists” who want to further an anti-LGBTQ agenda will do so. And it won’t make a bit of difference whether they follow the AP Stylebook or ignore it, because the meaning of a sentence–and an article–is is about how the words chosen for it interact, as well as their generally accepted meanings.