I liken the "union messaging problem" to what happenned to the Civil Rights Movement among many African-American families.
Our parents (in some cases grand-parents, but I date myself) marched, sang, prayed, got fired, beat, and kept fighting.
When we "overcame", our parents were reticient to pass on the stories of the struggle to their kids. So those kids grew up able to drink from whatever fountian was available and were able to seat in whatever seat they purchased. In their minds, the Movement was "necessary" but the fight had been won and the movement was ancient history.
So that is what they taught their kids ... If they taught they anything about the Movement.
Whereas, I doubt we will ever go back to the de jure crimes of jim crow, in the labor movement, we are seeing how quickly the hard fought gains can be eroded, because we did not teach our children.