The trifecta of topics not to discuss in polite company is religion, politics, and sex.
None of them gets close to the most sensitive topic of them all: Parenting.
Sex: Is not about you and the company you are in. It can be discussed from a titillating and dissociated place. The shame and guilt we carry do not need to be revealed in that conversation.
Politics: As much as we want to change the world through our views - in conversation, it is not about us. It is about them. What the Them has to do.
Religion: When you are entrenched in religion, your beliefs cannot be shaken, and you are safe to argue from a position of strong beliefs.
Here is the thing with parenting: It is intensely, and utterly, only about you. Our actions, our choices. What you do, and don't do, is all on you. You directly influence dependents in your life.
We are constantly second-guessing our beliefs and actions.
That shame and guilt will come through in every conversation. To discuss parenting is to discuss directly what you must do differently. Every conversation will reveal our fears and inadequacies.
Just ask a group of parents: "Pacifier, or no pacifier?"