One of the sufferings Fu Ping had to endure was to be forced to eat "bitter meal". She describes the scene on Page 37 of Bend, Not Break:
There was a big pot on the field into which the Red Guards began dumping dirt, animal dung, pieces of tree trunk, and anything else they could scoop off the ground. One of them scraped a sheet of yellow mold off a tree trunk and flung it into the pot with an evil cackle.
"This was what our ancestors ate," a female guard said loudly. "Our parents, grandparents, and great-grandparents suffered because your selfish families deprived them of good food. Today you will eat this bitter meal to remember our families' suffering."
That female guard's ancestors might have been deprived of good food, but they would not have eaten meals made of the things listed above.
Consuming "bitter meal" (忆苦饭) was an important ritual during the Cultural Revolution. But in contrary to Fu Ping's memory, it was not a punishment for "bad elements" or their children. It was an educational tool for all peoples in the society so they won't forget the sufferings of poor people in the "old society." If anything, the Red Guards and the "red elements" participated more eagerly to show their revolutionary zeal and they might even deny the opportunity for "bad elements" to participate.
The ingredients for "bitter meal" varied by places and time. They were typically made up of undesirable food items with spoiled meat and inedible vegetables, mimicking what poor people could have got in the old days. It was definitely not tasteful, but a far cry from animal dung.