This has to do with the First Lady of the US who is married to a man who won election at least partly because of his morality telling these jokes. That's what makes them inappropriate.
Ranch and farm humor is a little more earthy than your average uptight suburban moralist expects -- but that is normal for folks who deal with the daily realities of sanitation and reproduction. My great-grandmother, who was every inch a Southern lady, grew up on a rural plantation, and even SHE knew the "milk a bull" joke. And told it in my presence at least once (she died when I was 8.)
Mrs. Bush didn't use any bad language, and unless a person already knew the "facts of life" (e.g. the poor 4 year old child of liberals) the joke would go right over his head. That is the essence of "blue" humor - it isn't naughty unless you already know the score, so it goes right over the kids' heads. If you already know the score, you shouldn't be offended. And that sort of humor has always been permissible even for Southern ladies.
Her jokes weren't immoral. She's not immoral. Lynn Cheney is not immoral.
You really need to get over yourself. I grew up in the South with a Southern Baptist mother, Southern Baptist grandmothers ... etc. I could easily hear each one of them tell a joke like that "in polite company." Are you wanting the First Lady to continue in that mold that the Democrats were trying to put her in during the election? Remember Terezzzaaa's comments about Laura Bush not ever having a "real job"?
wonder if you'd be screaming so loud if it were Bill and Billary!