He said that he would get verbal agreement to sleep together before buying drinks. How is getting consent to have sex and then later having sex equivalent to s

He said that he would get verbal agreement to sleep together before buying drinks. How is getting consent to have sex and then later having sex equivalent to stabbing a friend in the back? I don’t understand the analogy. Unless you think one-night stands are morally wrong, I don’t really see any problems with his actions.