Apparently, a Christmas card addressed to "Mr. and Mrs. Hisfirstname Hislastname" is akin to a black man being called "boy." Nevermind that the first is the formal way to address an envelope to a couple, and the second is an out-and-out insult. For heaven's sake, people, whether you take your husband's last name or not, if someone calls you by it, they're not trying to point out how you're his chattel and all your honour comes through him!
Now, I can totally understand why a woman would choose not to take her husband's last name. Not an issue for me, and not much of one for most people. It's an accepted choice nowadays. But it has posed some problems for the writers of etiquette books, and they haven't come to a consensus on the correct way to address an envelope to a married couple with two last names - or if they have, the word clearly hasn't trickled down to most people. Newsflash: IT'S JUST A CHRISTMAS CARD. Or, IT'S JUST A WEDDING INVITATION. Nobody is trying to offend you or declare that the historical reality of a husband "owning" a wife is in any way true in your case. Get over it, and start fighting real battles for feminism if fight battles you must. Like, make sure that no woman ever gets fired for taking too much sick time to be with a sick baby. That's a battle worth fighting. This one - it's a meaningless historical relic.