As an anthropologist, I feel compelled to correct Tennis on the part about the incest taboo. Every culture has an incest taboo, but how incest is defined varies from culture to culture.
Ok, now on to this poor wife: she's poor because she doesn't have much affection coming her way in her life, and if she did, she wouldn't know how to handle it.
Just about every person has lips, and the way her husband uses them to kiss his mother probably isn't the same way he uses them toward her. She should know that and embrace it. It kinda reminds me of the time when parents explain to a child that many different kinds of love exist (i.e. love from parent to child isn't the same as romantic love between parents). Well, lady, different kinds of kisses exist, too!
And as many previous letter writers have written, she should seek some professional advice about her jealousy issues or about being ‘weirded out’ by her husband's behavior before ever bringing it up to him. (daugherofeli, response to post, Cary Tennis, “My husband kisses his mom on the lips,” Salon, 29 July 2009).
re: "Every culture has an incest taboo, but how incest is defined varies from culture to culture" (daughterofeli)
How incest is defined does vary from culture to culture. How true. Letter Writer, If you should happen upon other truths you find shocking owing to your evident naivety concerning cultural variety and meaning assessment, like if in fact it turns out your husband comes from a culture where every once in awhile moms put lips to penis, not just to mouth (different kinds of kisses! yay! blessed-be the glory and the wonderfulness!), please, too, go see a therapist and get yourself straightened out.
Please don't be thinking being an anthropologist means becoming a child-abuse apologist. It's true; but it's not their primary concern: They exist to catch sane people like you up.