The good news:
The Deer Lady of Copco Lake is out of jail!
The bad news: Crass jokes, for shock value, are still good for kicks anytime. When insecure people have to pick and poke just to provoke, it's pretty sad. But you still have to protect yourself from it.
Give your mom a chance to do it her way, but if necessary then insist you do it yours. This is your home and your life, so you choose and make it what you want, regardless. As much as I hate these people I like your idea of frank, direct, honest conversation. It comes from the heart.
If that doesn't work, maybe find a topic THEY are sensitive or sore about. "How's your wife's weird skin condition? Has your husband stopped sleeping around, or beating the kids? Is your son out of jail yet? Have you heard about these cloth tampons you can boil and keep using over and over? They smell bad, but what do you think? Let's TALK about feminine hygiene!"
I don't know what these people would feel really uncomfortable or upset talking about, but your self-defense may include some good offense!
Or fish some books for ideas:
The Gentle Art of Verbal Self-Defense
You Can't Say That To Me
Emotional Vampires
Despite all our eager advice, I suspect (and hope!) you'll end up finding your particular way...