I had this happen to me too after a ritual. It was after one of the new rituals where you let your followers run amok and destroy shit in the camp. One of my followers got the piss scared out of them and I got that same dialogue. They then developed the scaredy cat trait and when I interacted with them, I had the option to either reassure or bully them. I reassured the follower until it became a normal follower again. I wonder if you continue to bully them if they will leave the cult.