So here's the question: If your parents do/say something that offends your partner, whose job is it to address the issue with the parents?
I'm going to go into this argument with the assumption that we're talking about a couple of grown adults. As such, if your in-laws have done something to offend you it is YOUR job to address the problem. Obviously you would like your spouse to back you up, but putting your partner in the middle of your issues is unfair. That's not all, having your partner do your dirty makes you look like you're trying to drive a wedge between your spouse and his/her parents.
Do you really need your husband to tell his mother that it hurts your feelings when she criticizes your hairstyle? Is it necessary to have your wife tell her father that you get upset when he tries to tell you how to chop wood? Negative and negative. You should always be able to count on your spouse to have your back, but that doesn't mean you put them in the line of fire.
You're not the horrible old bat I always thought you were!
Awww, well if I had known you were a big Cry-baby-Sally I never would have said your outfit makes you look like a $3 hooker!
Shane, tell me why you think it's your duty to fight your partners battle with your parents (well not YOU specifically).