The culture is just so trashed at this point that this kind of gutter humor fails to raise eyebrows. Truly evidence of the debasement of our culture.
Yes, the First Lady telling a harmless joke that's been told on countless farms countless times over a countless number of years is a sure sign we're turning into Sodom and Gomorrah. I'd be willing to bet you could find that particular joke in Reader's Digest in the early or middle part of the 1900s. But then, Reader's Digest is truly evident of the debasement of our culture, I guess.
Worse are the "moderates" here and elsewhere who raise the straw man of Christian prudery to defend the indefensible. Irrespective of religious beliefs, societal norms have dictated that there should be a difference between a joke that a First Lady would tell in a public forum, and jokes that make the rounds of locker rooms and pool halls. The line that separate such things are also the lines that separate us from barbarism.